Kliem, M. (1977). Friedrich Engels. Philipp Reclam jun..
Lua i Stíl Chicago (17ú heag.)Kliem, Manfred. Friedrich Engels. Leipzig: Philipp Reclam jun., 1977.
Lua MLA (8ú heag.)Kliem, Manfred. Friedrich Engels. Philipp Reclam jun., 1977.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.