title: Feline fibrosarcoma virus: quantitative focus assay, focus morphology and evidence for a "helper virus".
mesh_terms: D000818:Animals; D002415:Cats; D002449:Cell Aggregation; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells; D005347:Fibroblasts; D000882:Haplorhini; D006378:Helper Viruses / Q000302:isolation & purification; D008168:Lung; D009858:Oncogenic Viruses / Q000032:analysis*