scholarly article by David S. Johnson published December 1974 in Journal of Computer and System Sciences

scientific article published in 1997

scientific article published in December 1975

scientific article

book

scientific article published in 1974

scientific article published in 1988

scientific article published in 1983

scientific article published in 2006

scientific article published in 1976

article by Michael Garey et al published February 1976 in Theoretical Computer Science

scientific article published in 1976

scientific article published in June 1977

scientific article published in 1977