Barrera Sànchez, K. M., Escalante, J. A., Cerna Hernàndez, J. A., Duarte Aguirre, S. E., Guerra Lima, D. E., & Rodrìguez Rivera, L. C. (2015). A comparative research on the effectiveness of using student - centered instruction with teacher - centered instructions for the development of the english speaking skill with eleventh grade students in sections "E" and "H" at Centro Escolar INSA during 2015. Santa Ana, El Salvador: Universidad de El Salvaor.

Barrera Sànchez, Karla Margarita, Juan Antonio Escalante, Jenifer Antonia Cerna Hernàndez, Sofìa Elizabeth Duarte Aguirre, David Edgardo Guerra Lima, and Luisa Catalina Rodrìguez Rivera. A Comparative Research On the Effectiveness of Using Student - Centered Instruction With Teacher - Centered Instructions for the Development of the English Speaking Skill With Eleventh Grade Students in Sections "E" and "H" At Centro Escolar INSA During 2015. Santa Ana, El Salvador: Universidad de El Salvaor, 2015.

Barrera Sànchez, Karla Margarita, et al. A Comparative Research On the Effectiveness of Using Student - Centered Instruction With Teacher - Centered Instructions for the Development of the English Speaking Skill With Eleventh Grade Students in Sections "E" and "H" At Centro Escolar INSA During 2015. Santa Ana, El Salvador: Universidad de El Salvaor, 2015.