Tissue culture assay of helper activity of murine leukemia virus for murine sarcoma virus.
D000818:Animals; D001358:Avian Sarcoma Viruses; D001681:Biological Assay; D046508:Culture Techniques; D005347:Fibroblasts; D006378:Helper Viruses; D009052:Leukemia Virus, Murine; D008722:Methods; D051379:Mice; D012513:Sarcoma, Experimental