Richmond, P. G. (1981). Piaget (2a ed.). Ibrasa.
Lua i Stíl Chicago (17ú heag.)Richmond, Peter Graham. Piaget. 2a ed. Ibrasa, 1981.
Lua MLA (8ú heag.)Richmond, Peter Graham. Piaget. 2a ed. Ibrasa, 1981.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.