[Virological considerations on the diversity of leukemic virus in chicken].
D001355:Alpharetrovirus / Q000302:isolation & purification*; D000818:Animals; D001353:Avian Leukosis / Q000209:etiology / Q000382:microbiology*; D001358:Avian Sarcoma Viruses / Q000302:isolation & purification; D002645:Chickens