Esquivel Saldaña, M. A., & Espinosa Vega, . K. D. (2014). "Transfer occurrences in the use of English prepositions (in, on, at, over, to, for, by) among eight graders at Colegio Básico General San Mateo, David, 2014". David, Panamá: UDELAS.

Esquivel Saldaña, Marvin Ameth, and Katherine Dennisse Espinosa Vega. "Transfer Occurrences in the Use of English Prepositions (in, On, At, Over, To, For, By) Among Eight Graders At Colegio Básico General San Mateo, David, 2014". David, Panamá: UDELAS, 2014.

Esquivel Saldaña, Marvin Ameth, and Katherine Dennisse Espinosa Vega. "Transfer Occurrences in the Use of English Prepositions (in, On, At, Over, To, For, By) Among Eight Graders At Colegio Básico General San Mateo, David, 2014". David, Panamá: UDELAS, 2014.