Não informado. (1979). Focus on Learning Problems in Mathematics. Center for Teaching Learning on Mathematics.
Lua i Stíl Chicago (17ú heag.)Não informado. Focus on Learning Problems in Mathematics. Framingham, Mass: Center for Teaching Learning on Mathematics, 1979.
Lua MLA (8ú heag.)Não informado. Focus on Learning Problems in Mathematics. Center for Teaching Learning on Mathematics, 1979.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.