Quantification of steady-state operant behaviour : proceedings of the International Symposium on Recent Developments in the Quantification of Steady-State Operant Behaviour held at Owens Park, Manchester, on 22nd-25th July, 1980 - Bradshaw, Christopher M.; Szabadi, Elmer; Lowe, C. F. (Elsevier/North-Holland Biomedical Press, 1981)