Acuña Aguilar, E., Quirós Cordero, J., Gordon Zamora, J., & Palacios Palacios, S. (2017). Implementation of the multistage frame technique to enhance students' pronunciation of standard american english vowel sounds in group 10-1A at Canaán High School: A case study. Pérez Zeledón, Costa Rica: E. Acuña C..

Acuña Aguilar, Elian,, Johanna Quirós Cordero, Joshua Gordon Zamora, and Sandra Palacios Palacios. Implementation of the Multistage Frame Technique to Enhance Students' Pronunciation of Standard American English Vowel Sounds in Group 10-1A At Canaán High School: A Case Study. Pérez Zeledón, Costa Rica: E. Acuña C., 2017.

Acuña Aguilar, Elian,, Johanna Quirós Cordero, Joshua Gordon Zamora, and Sandra Palacios Palacios. Implementation of the Multistage Frame Technique to Enhance Students' Pronunciation of Standard American English Vowel Sounds in Group 10-1A At Canaán High School: A Case Study. Pérez Zeledón, Costa Rica: E. Acuña C., 2017.