Leedy Paul D. (2001). Practical Research Planning and Design. Merrill Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Leedy Paul D. Practical Research Planning and Design. MPH: Merrill Prentice Hall, 2001.
Lua MLA (9ú heag.)Leedy Paul D. Practical Research Planning and Design. Merrill Prentice Hall, 2001.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.