. "1999Z"^^ . . . "Gross, Ludwik"@en . . "1904-09-11Z"^^ . "1999-07-19Z"^^ . . . . . . . . . . "Ludwik Gross (September 11, 1904 - July 19, 1999) was a Polish-American virologist who discovered two different tumor viruses, murine leukemia virus and mouse polyomavirus, capable of causing cancers in laboratory mice."@en . . . "Ludwik Gross"@en . . . "1904Z"^^ . "American virologist" . .