Grupo de Pesquisa em Jogos

Resumo

Publicações não vinculadas com os projetos acima.

Publicações

Conferência

2025

11/08/2025 • Ticianne Darin, Kamila Rodrigues, Georgia da Cruz Pereira, Diego E. Ricca, Leonardo T. Pereira
IV Workshop on Interaction and User Research in Game Development (WIPlay)

Palavras-chave: human-computer interaction, digital games
Abstract • BibTeX • Full Paper

Abstract
Recognizing digital games as a significant global cultural force offering diverse opportunities across entertainment, education, health, and other domains, the international Human-Computer Interaction community has focused on game research. However, a need persists to bridge geographical contexts and foster cross-disciplinary collaboration. To address this, the fourth edition of WIPlay has evolved from three successful Brazilian national workshops into an international platform at INTERACT 2025. We broadened its scope by incorporating diverse cultural perspectives on player experience, inclusive design, and global challenges in the gaming industry. By attracting international HCI researchers, game developers, and game user researchers, WIPlay provides a collaborative space for discussing, exploring, and defining future directions for the field.
BibTeX • Copiar
```
@InProceedings{10.1007/978-3-032-05008-3_71,
author="Darin, Ticianne
and Rodrigues, Kamila
and Pereira, Georgia da Cruz
and Ricca, Diego En{\'e}as
and Pereira, Leonardo T{\'o}rtoro",
editor="Ardito, Carmelo
and Diniz Junqueira Barbosa, Simone
and Conte, Tayana
and Freire, Andr{\'e}
and Gasparini, Isabela
and Palanque, Philippe
and Prates, Raquel",
title="IV Workshop on Interaction and User Research in Game Development (WIPlay)",
booktitle="Human-Computer Interaction -- INTERACT 2025",
year="2026",
publisher="Springer Nature Switzerland",
address="Cham",
pages="382--388",
isbn="978-3-032-05008-3"
}
```
11/08/2025 • Pedro R. Rocha, Leonardo T. Pereira, Claudio F. M. Toledo
Evolutionary Boss Improvement in Doom

Palavras-chave: games, generative systems, genetic algorithm, heuristics, representation
Abstract • BibTeX • Full Paper

Abstract
Automating part of enemy balancing may save precious resources for developers, allowing them to focus on more creative tasks, while also enabling developers to create enemies that cater to specific kinds of players. In this paper, we adapt the 'Evolutionary Boss Improvement' (EBI) method to the DOOM game, modifying the Cyberdemon enemy. This increases the method's generality by testing its effectiveness in another game genre. By implementing the EBI pipeline with appropriate adaptations to the encoding, decoding, crossover and mutation algorithms, we were able to improve the fitness of our enemies, which was evaluated by having a set percentage of remaining health after testing with bots. We asked anonymous volunteers to play the game against either the original Cyberdemon or our modified version (evolved using EBI) and to fill a survey about their experience, allowing us to assess their opinions about the boss fight. The version each player fought was randomly selected when starting the game, making it a double-blind experiment. The results indicate we created an individual with a similar feel to the original, maintaining player satisfaction, whilst also requiring less manpower from the developer.
BibTeX • Copiar
```
@inproceedings{rocha:2025,
author = {Rocha, Pedro Regattieri and Pereira, Leonardo T\'{o}rtoro and Toledo, Cl\'{a}udio Fabiano Motta},
title = {Evolutionary Boss Improvement in Doom},
year = {2025},
isbn = {9798400714641},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3712255.3726718},
doi = {10.1145/3712255.3726718},
booktitle = {Proceedings of the Genetic and Evolutionary Computation Conference Companion},
pages = {891–894},
numpages = {4},
keywords = {games, generative systems, genetic algorithm, heuristics, representation},
location = {NH Malaga Hotel, Malaga, Spain},
series = {GECCO '25 Companion}
}
```
30/09/2024 • Leonardo T. Pereira, Orlando A. Figueiredo, Kamila R. H. Rodrigues, Kalinka C. Branco, Claudio F. M. Toledo
Re-G3X: Pesquisa em jogos, gamificação, jogos sérios e XR

Palavras-chave: Procedural Content Generation, Artificial Intelligence, Serious Games, Human-Computer Interaction, Gamification
Abstract • BibTeX • Full Paper

Abstract
O artigo apresenta o grupo de pesquisa ReG3X (Pesquisa em Jogos, Gamificaçao, Jogos Sérios, e Realidade Estendida) Este é um grupo recente, criado com a parceria do ICMC-USP e IGCE-UNESP, bem como parceiros de outros institutos. O grupo de pesquisa sobre geraçao procedural de conteúdo e outros usos de Inteligência Artificial, Engenharia de Software, Interaçao Humano-Computador em jogos, além de jogos sérios e gamificaç ao. Apesar de recente, o grupo tem publicaçoes em revistas como Expert System with Applications, Soft Applied Computing, IEEE Transactions on Games e Interacting with Computers, e conferências como like IEEE Conference on Games, Congress on Evolutionary Computation, CHI Conference on Human Factors in Computing Systems e SBGames.
BibTeX • Copiar
```
@inproceedings{reg3x:2024,
author = {Leonardo Pereira and Orlando Figueiredo and Kamila Rodrigues and Kalinka Branco and Claudio Toledo},
title = {Re-G3X: Pesquisa em jogos, gamificação, jogos sérios e XR},
booktitle = {Anais do XXIII Simpósio Brasileiro de Jogos e Entretenimento Digital},
location = {Manaus/AM},
year = {2024},
publisher = {SBC},
address = {Porto Alegre, RS, Brasil},
url = {https://sbgames.org/sbgames2024/wp-content/uploads/2024/09/241754_2.pdf}
}
```
30/09/2024 • Pedro Michalichem, Leonardo Pereira, Kamila Rodrigues
Task Complete: A gamified solution to exercise positive habits in players with Intellectual Disabilities

Palavras-chave: Gamified Web Solution, Task Complete, Game Design, Game Evaluation, Accessibility, Intellectual Disability
Abstract • BibTeX • Full Paper

Abstract
This paper describes creating and evaluating a gamified solution called Task Complete, which aims to support productivity and encourage positive habits in its players, especially people with Intellectual Disabilities. The solution transforms everyday tasks into motivational elements, engaging users through virtual rewards. It was designed following principles of User Centered Design, as well as developed and evaluated considering accessibility and usability requirements. The PENS model and Web Content Accessibility Guidelines (WCAG)1 were considered in the project, seeking to make the solution inclusive for various user profiles.
BibTeX • Copiar
```
@inproceedings{michalichem:2024,
author = {Pedro Michalichem and Leonardo Pereira and Kamila Rodrigues},
title = { Task Complete: A gamified solution to exercise positive habits in players with Intellectual Disabilities},
booktitle = {Anais do XXIII Simpósio Brasileiro de Jogos e Entretenimento Digital},
location = {Manaus/AM},
year = {2024},
keywords = {},
issn = {0000-0000},
pages = {474--495},
publisher = {SBC},
address = {Porto Alegre, RS, Brasil},
doi = {10.5753/sbgames.2024.241189},
url = {https://sol.sbc.org.br/index.php/sbgames/article/view/32331}
}
```
30/09/2024 • Laura Scotelari, Matheus Luccas, Leonardo Pereira, Kalinka Branco
Comunicação Eficaz em Games: Utilização de Elementos Visuais no Design de Jogos

Palavras-chave: Elementos pictóricos, Estética, Respostas emocionais, Games, Serious Games
Abstract • BibTeX • Full Paper

Abstract
Em jogos, atenção aos elementos artísticos melhoram a transmissão da informação. Este trabalho explora técnicas para integrar o desenvolvimento de jogos com escolhas artísticas adequadas. Elementos pictóricos como cores, linhas, texturas e formas devem ser cautelosamente selecionados para garantir correto entendimento do jogo e seu conteúdo educacional. O mesmo se aplica à criação de personagens e interfaces. Também é discutido como integrar técnicas do Construtivismo nessas decisões pode promover aprendizado ativo e eficaz em jogos sérios, ao escolher cuidadosamente elementos de apresentação direcionado ao engajamento e retenção dos jogadores, favorecendo o uso de jogos no ensino.
BibTeX • Copiar
```
@inproceedings{scotelari:2024b,
author = {Laura Scotelari and Matheus Luccas and Leonardo Pereira and Kalinka Branco},
title = { Comunicação Eficaz em Games: Utilização de Elementos Visuais no Design de Jogos},
booktitle = {Anais do XXIII Simpósio Brasileiro de Jogos e Entretenimento Digital},
location = {Manaus/AM},
year = {2024},
keywords = {},
issn = {0000-0000},
pages = {216--228},
publisher = {SBC},
address = {Porto Alegre, RS, Brasil},
doi = {10.5753/sbgames.2024.241284},
url = {https://sol.sbc.org.br/index.php/sbgames/article/view/32311}
}
```
30/09/2024 • Leonardo T. Pereira, Kamila R. H. Rodrigues, Claudio F. M. Toledo, T. Yuji Teoi,
Understanding players to enhance their fun: how to extract player data and motivation factors for procedural content generation

Palavras-chave: Player Modeling, Player Behavior, User Profiling, Digital Games, Procedural Content Generation
Abstract • BibTeX • Full Paper

Abstract
This paper uses results from recent literature on player data collection and Human-Computer Interaction (HCI) fundamentals to classify the data collected by gaming systems to identify different types of players and their motivators. Our study proposes to address the lack of standards and ambiguous identification of data and collection techniques, which hinders progress in the Procedural Content Generation field. Our proposed classification may help researchers and game developers build metrics to evaluate users' motivators and player types, fostering the chance to generate game content to optimize performance, fun, and user satisfaction when playing.
BibTeX • Copiar
```
@inproceedings{pereira:2024:sbgames,
author = {Leonardo Pereira and Kamila Rodrigues and Claudio Toledo and T. Teoi},
title = { Understanding players to enhance their fun: how to extract player 
data and motivation factors for procedural content generation},
booktitle = {Anais Estendidos do XXIII Simpósio Brasileiro de Jogos e Entretenimento Digital},
location = {0},
year = {2024},
keywords = {},
issn = {0000-0000},
pages = {37--42},
publisher = {SBC},
address = {Porto Alegre, RS, Brasil},
doi = {10.5753/sbgames_estendido.2024.241181},
url = {https://sol.sbc.org.br/index.php/sbgames_estendido/article/view/32001}
}
```

2021

20/12/2021 • Leonardo T. Pereira, Breno M. F. Viana, Claudio F. M. Toledo
Procedural Enemy Generation through Parallel Evolutionary Algorithm

Palavras-chave: enemy generation, procedural content generation, video games, parallel evolutionary algorithm
Abstract • BibTeX • Full Paper

Abstract
This paper uses results from recent literature on player data collection and Human-Computer Interaction (HCI) fundamentals to classify the data collected by gaming systems to identify different types of players and their motivators. Our study proposes to address the lack of standards and ambiguous identification of data and collection techniques, which hinders progress in the Procedural Content Generation field. Our proposed classification may help researchers and game developers build metrics to evaluate users' motivators and player types, fostering the chance to generate game content to optimize performance, fun, and user satisfaction when playing.
BibTeX • Copiar
```
@INPROCEEDINGS{9637547,
  author={Pereira, Leonardo T. and Viana, Breno M. F. and Toledo, Claudio F. M.},
  booktitle={2021 20th Brazilian Symposium on Computer Games and Digital Entertainment (SBGames)}, 
  title={Procedural Enemy Generation through Parallel Evolutionary Algorithm}, 
  year={2021},
  volume={},
  number={},
  pages={126-135},
  keywords={Machine learning algorithms;Weapons;Impedance matching;Loading;Prototypes;Entertainment industry;
  Games;enemy generation;procedural content generation;video games;parallel evolutionary algorithm},
  doi={10.1109/SBGames54170.2021.00024}}
```

2019

28/10/2019 • Fabrício G. Faria, Leonardo T. Pereira, Cláudio Toledo
Adaptive Generation of Characters for Tabletop Role Playing Games

Palavras-chave: evolutionary algorithm, procedural content generation, character generation, tabletop, RPG, user input
Abstract • BibTeX • Full Paper

Abstract
This paper tries to solve the problem where automated character creation for Tabletop RPGs is completely random and does not fully pleases certain players, especially those that have difficulty in being creative and adapting characters to their personal tastes. To accomplish that, the usage of a Evolutionary Algorithm (EA) was proposed, in conjunction with the user's input (positive or negative) during generations, to create characters focused on having traits that are catered to each individual's taste. The generated traits are 'Race', 'Class', 'Size', 'Visual Trait', 'Personality' and 'Quirk'. The fitness calculation for each individual was made using trait tables with weights previously defined by the programmer, and posteriorly by the user's evaluation of the characters during execution. The project was made using the Unity game engine with C# language, to take advantage of the tool's easy interface creation. It was produced as a phone application, for ease of distribution and general use. The application was tested with a variety of users, and the results, presented in the form of graphs, indicate that the rejection rate was almost null, with the great majority of users recognizing the gradual improvement of suggestions between generations, and evaluating positively the characters generated by the algorithm.
BibTeX • Copiar
```
@INPROCEEDINGS{faria:2019:sbgames,
  author={Faria, Fabrício Guedes and Pereira, Leonardo Tórtoro and Toledo, Cláudio Fabiano Motta},
  booktitle={2019 18th Brazilian Symposium on Computer Games and Digital Entertainment (SBGames)}, 
  title={Adaptive Generation of Characters for Tabletop Role Playing Games}, 
  year={2019},
  volume={},
  number={},
  pages={39-46},
  keywords={Games;Generators;Phonocardiography;Machine learning algorithms;
  Character generation;Computational modeling;Evolutionary computation;evolutionary algorithm;
  procedural content generation;character generation;tabletop RPG;user input},
  doi={10.1109/SBGames.2019.00016}}
```
29/10/2018 • Leonardo T. Pereira, Fernando H. C. Silva, Paula T. Palomino, Seiji Isotani
A abordagem construtivista no desenvolvimento de um serious game do gênero escape room

Palavras-chave: Construtivismo, Serious Games, Aprendizagem baseada em Jogos Digitais, Escape Room, Lógica de Programação
Abstract • BibTeX • Full Paper

Abstract
O presente trabalho apresenta uma pesquisa e experimento na área de aprendizagem baseada em jogos digitais, utilizando-se da abordagem construtivista para o desenvolvimento de um serious game educacional do gênero escape room cujo objetivo é ensinar conceitos básicos de lógica de programação para estudantes que nunca tiveram contato com a área. O experimento consistiu da aplicação de questionário pré-teste, intervenção com a interação dos alunos com o game e questionário pós-teste, a fim de verificar dois aspectos da aprendizagem: a assimilação do conteúdo em si e a transferência de conhecimento.
BibTeX • Copiar
```
@inproceedings{pereira:2018,
author = {Pereira, Leonardo and Silva, Fernando and Toledo Palomino, Paula and Toledo, Claudio and Isotani, Seiji},
year = {2018},
month = {11},
pages = {},
title = {A abordagem construtivista no desenvolvimento de um serious game do gênero escape room}
}
```
04/10/2018 • Leonardo T. Pereira, Paulo V. S. Prado, Claudio Toledo
Evolving Dungeon Maps With Locked Door Missions

Palavras-chave:
Abstract • BibTeX • Full Paper

Abstract
The present paper proposes an evolutionary algorithm for procedural content generation of dungeon maps together with locked door missions. The algorithm evolves a tree structure which contains information of a dungeon. The aim is to converge the generated dungeons as close as possible to the input configuration set by a game designer. The dungeon holds information about rooms such as their number, connections between them and position in a 2D map (also knows as grid). It also contains relevant semantic information for generating narrative properties in the dungeon. Those are the placement of keys and locks in it, in a feasible way. Results show the algorithm is able to create dungeons within the desired configurations for a large set of different inputs. Also, they show the generated maps are perceived as human-designed, and evoke similar opinions of fun and difficulty when compared to human-designed maps.
BibTeX • Copiar
```
@INPROCEEDINGS{pereira:2018:cec,
  author={Pereira, Leonardo T. and Prado, Paulo V.S. and Toledo, Claudio},
  booktitle={2018 IEEE Congress on Evolutionary Computation (CEC)}, 
  title={Evolving Dungeon Maps With Locked Door Missions}, 
  year={2018},
  volume={},
  number={},
  pages={1-8},
  keywords={Games;Vegetation;Space missions;Semantics;Two dimensional displays;Layout;Task analysis},
  doi={10.1109/CEC.2018.8477718}}
```

2016

06/11/2016 • Leonardo T. Pereira, Claudio Toledo, Lucas N. Ferreira, Levi H.S. Lelis
Learning to Speed Up Evolutionary Content Generation in Physics-Based Puzzle Games

Palavras-chave: Evolutionary Algorithm, Machine Learning, Procedural Content Generation, Classification, Video Game
Abstract • BibTeX • Full Paper

Abstract
Procedural content generation (PCG) systems are designed to automatically generate content for video games. PCG for physics-based puzzles requires one to simulate the game to ensure feasibility and stability of the objects composing the puzzle. The major drawback of this simulation-based approach is the overall running time of the PCG process, as the simulations can be computationally expensive. This paper introduces a method that uses machine learning to reduce the number of simulations performed by an evolutionary approach while generating levels of Angry Birds, a physics-based puzzle game. Our method uses classifiers to verify the stability and feasibility of the levels considered during search. The fitness function is computed only for levels that are classified as stable and feasible. An approximation of the fitness that does not require simulations is used for levels that are deemed as unstable or unfeasible by the classifiers. Our experiments show that naively approximating the fitness values can lead to poor solutions. We then introduce an approach in which the fitness values are approximated with the average fitness value of the levels' parents added to a penalty value. This approximation scheme allows the search procedure to find good-quality solutions much more quickly than a competing approach-we reduce from 43 to 25 minutes the running time required to generate one level of Angry Birds.
BibTeX • Copiar
```
@INPROCEEDINGS{pereira:2016,
  author={Pereira, Leonardo T. and Toledo, Claudio and Ferreira, Lucas N. and Lelis, Levi H.S.},
  booktitle={2016 IEEE 28th International Conference on Tools with Artificial Intelligence (ICTAI)}, 
  title={Learning to Speed Up Evolutionary Content Generation in Physics-Based Puzzle Games}, 
  year={2016},
  volume={},
  number={},
  pages={901-907},
  keywords={Conferences;Artificial intelligence;Evolutionary Algorithm;Machine Learning;
  Procedural Content Generation;Classification;Video Game},
  doi={10.1109/ICTAI.2016.0139}}
```

2014

12/07/2014 • Lucas Ferreira, Leonardo T. Pereira, Claudio Toledo, Rodrigo Pereira
Evolutionary approaches to evolve AI scripts for a RTS game

Palavras-chave: real time strategy, games, evolutionary algorithms, artificial intelligence
Abstract • BibTeX • Full Paper

Abstract
This paper evaluates three different Evolutionary Algorithms (EAs) for generating non-player characters (NPCs) via Artificial Intelligence scripts for a Real Time Strategy (RTS) game. The first approach executes only a Genetic Algorithm (GA), while the second and third ones combine GA with a Dynamic Scripting approach. The Bos Wars game is used for testing these EAs, which are able to create and to evolve strategies of this RTS game coded as scripts in LUA language. In order to do this, the EA communicates with Bos Wars' engine by sending scripts, playing matches and capturing statistical data to evaluate its individuals.
BibTeX • Copiar
```
@inproceedings{10.1145/2598394.2598486,
author = {Ferreira, Lucas and Pereira, Leonardo and Toledo, Claudio and Pereira, Rodrigo},
title = {Evolutionary approaches to evolve AI scripts for a RTS game},
year = {2014},
isbn = {9781450328814},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/2598394.2598486},
doi = {10.1145/2598394.2598486},
booktitle = {Proceedings of the Companion Publication of the 2014 Annual Conference on Genetic and Evolutionary Computation},
pages = {47–48},
numpages = {2},
keywords = {real time strategy, games, evolutionary algorithms, artificial intelligence},
location = {Vancouver, BC, Canada},
series = {GECCO Comp '14}
}
```
12/07/2014 • Lucas Ferreira, Leonardo T. Pereira, Claudio Toledo
A multi-population genetic algorithm for procedural generation of levels for platform games

Palavras-chave: super mario bros, procedural content generation, platform, genetic algorithm, games
Abstract • BibTeX • Full Paper

Abstract
This paper presents a multi-population genetic algorithm for procedural generation of levels for platform games such as Super Mario Bros (SMB). The algorithm evolves four aspects of the game during its generations: terrain, enemies, coins and blocks. Each aspect has its own codification, population and fitness function. At the end of the evolution, the best four aspects are combined to construct the level. The method has as input a vector of parameters to configure the characteristics of each aspect. Experiments were made to evaluate the capability of the method in generating interesting levels. Results showed the method can be controlled to generate different types of levels.
BibTeX • Copiar
```
@inproceedings{10.1145/2598394.2598489,
author = {Ferreira, Lucas and Pereira, Leonardo and Toledo, Claudio},
title = {A multi-population genetic algorithm for procedural generation of levels for platform games},
year = {2014},
isbn = {9781450328814},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/2598394.2598489},
doi = {10.1145/2598394.2598489},
booktitle = {Proceedings of the Companion Publication of the 2014 Annual Conference on Genetic and Evolutionary Computation},
pages = {45–46},
numpages = {2},
keywords = {super mario bros, procedural content generation, platform, genetic algorithm, games},
location = {Vancouver, BC, Canada},
series = {GECCO Comp '14}
}
```

Revista

12/02/2022 • Breno M.F. Viana, Leonardo T. Pereira, Claudio F.M. Toledo, Selan R. dos Santos, Silvia M.D.M. Maia
Feasible–Infeasible Two-Population Genetic Algorithm to evolve dungeon levels with dependencies in barrier mechanics

Palavras-chave: Level generation, Procedural content generation, Barrier mechanics, Video games, Constrained optimization
Abstract • BibTeX • Full Paper

Abstract
This paper presents a search-based solution for the generation of dungeon levels with barrier mechanics and the placement of challenges and rewards in the levels’ rooms. The barrier is a feature that temporarily blocks the player’s progression, where one or more keys will unblock the way. The placement of barriers and keys must satisfy some constraints since the player cannot be stuck during the gameplay. Feasible–Infeasible Two-Population Genetic Algorithm (FI2Pop GA) evolves a grid representation that handles the level dependencies of barrier mechanics. We propose the concept of ordered regions to control the availability of keys better in the levels and procedures to create levels with more diversity in their contents. Data to measure the variety of the generated content is collected based on map linearity, mission linearity, leniency, and path redundancy. We analyzed our results through expressive range analysis, and it shows that our approach can generate a wide variety of playable levels.
BibTeX • Copiar
```
@article{viana:2022,
title = {Feasible–Infeasible Two-Population Genetic Algorithm to evolve dungeon levels with dependencies in barrier mechanics},
journal = {Applied Soft Computing},
volume = {119},
pages = {108586},
year = {2022},
issn = {1568-4946},
doi = {https://doi.org/10.1016/j.asoc.2022.108586},
url = {https://www.sciencedirect.com/science/article/pii/S1568494622000989},
author = {Breno M.F. Viana and Leonardo T. Pereira and Claudio F.M. Toledo and Selan R. {dos Santos} and Silvia M.D.M. Maia},
keywords = {Level generation, Procedural content generation, Barrier mechanics, Video games, Constrained optimization}  
}
```

2017

20/10/2017 • Leonardo T. Pereira, Claudio F.M. Toledo
Speeding up Search-Based Algorithms for Level Generation in Physics-Based Puzzle Games

Palavras-chave: Search-based algorithms, machine learning, procedural content generation, classification, video game
Abstract • BibTeX • Full Paper

Abstract
This research uses Machine Learning (ML) techniques in order to aid search-based (SB) algorithms to improve level generation for physics-based puzzle games. These algorithms’ performance are improved by reducing simulation time when the ML techniques are applied. Classification algorithms prevent levels with undesired traits to be evaluated during the simulation phase of the SB procedures. An Angry Birds clone is used for conducting the experiments and results report improvement using the combined approach against every SB algorithm by itself.
BibTeX • Copiar
```
@article{pereira:2017,
author = {Pereira, Leonardo T. and Toledo, Claudio F. M.},
title = {Speeding up Search-Based Algorithms for Level Generation in Physics-Based Puzzle Games},
journal = {International Journal on Artificial Intelligence Tools},
volume = {26},
number = {05},
pages = {1760019},
year = {2017},
doi = {10.1142/S0218213017600193},
URL = {     
        https://doi.org/10.1142/S0218213017600193
},
eprint = { 
    
        https://doi.org/10.1142/S0218213017600193
}
}
```