PNAS73(9),3000–3004 (1976), DOI10.1073/pnas.73.9.3000. Abstract and micrographs: EcoRI-linearized colicinE1 DNA; crossed paired-length forms, wild-type/RecB-C versus RecA-deficient comparison. pmc.ncbi.nlm.nih.gov/articles/PMC430907/ . Author initials retained as verified.