by Robert U. Ayres ... [et al.]. by Robert E. Burk ...[et al.]. by Robert V. Pole ...[et al.]. by Robert F. Trapp ...[et al.]. by Robert K. Brayton ... [et al.]. by Robert M. Johnston ... [et al.]. by Roberto Serra ...[et al.]. by Robert E. Baldwin ...[et al.]. edited by J. C. Ayres ...[et al.]. by Robert A. Hall.