Caldas Cueva, Miguel, and Ratnesh Kumar Saraf. 2017. “Preserving Fuzzy Sg-Closed Sets Conservando Conjuntos Fuzzy Sg-Cerrados”. Proyecciones (Antofagasta, On Line) 20 (2):127-38. https://doi.org/10.4067/S0716-09172001000200001.