Videocassettes in education and training : proceedings of a conference organised by the Association for Programmed Learning and Educational Technology in conjuction with the Programmed Instruction Centre, Middlesex Polytechnic. Held at Enfield College, Middlesex Polytechnic, July 4th 1973. - Leedham, J.; Romiszowski, A. J. (Association for Programmed Learning and Educational Technology (APLET Occasional Publication), 1973)