LC data base 1-18-89 (hdg.: Butterworth, Michael, 1924- ; usage: Michael Butterworth, Sarah Kemp, Carola Salisbury)
Biog. resource center (Contemporary authors), June 17, 2004 (Michael Butterworth; b. Jan. 10, 1924, England; d. Oct. 1986; also known as: Robert Challoner, Carola Salisbury, William Dobson, Sarah Kemp, Michael Marlowe; no listing of works written as Robert Challoner, William Dobson, or Michael Marlowe)
Dobson, W. The ripper, 1981 t.p. (William Dobson); copyright statement (Michael Butterworth)