Lewis, N. R. (1974). An investigation of the difficulties experienced by students at a tertiary institution in Papua New Guinea. Dept. of Education, Research Branch.
Lua i Stíl Chicago (17ú heag.)Lewis, N. R. An Investigation of the Difficulties Experienced by Students at a Tertiary Institution in Papua New Guinea. Konedobu: Dept. of Education, Research Branch, 1974.
Lua MLA (9ú heag.)Lewis, N. R. An Investigation of the Difficulties Experienced by Students at a Tertiary Institution in Papua New Guinea. Dept. of Education, Research Branch, 1974.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.