Primary first-person research recollection by Joe M. McCord, dated24March1981 and published Citation Classics27April1981. Page1 explains xanthine-oxidase/cytochrome-c experiments, free-solution superoxide, contaminating dismutase in protein preparations and the1969 isolation/assay paper (JBC244,6049–6055). Full name printed in the commentary; no birth date inferred. Original1969 publisher PDF returned403, so historical description is explicitly based on this researcher account.