Harper, D. (1989). Logo: Theory & practice. Brooks/Cole.
Lua i Stíl Chicago (17ú heag.)Harper, Dennis. Logo: Theory & Practice. Pacific Grove, Calif: Brooks/Cole, 1989.
Lua MLA (9ú heag.)Harper, Dennis. Logo: Theory & Practice. Brooks/Cole, 1989.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.