by Roberto Serra ... [et al.]. by Robert U. Ayres ... [et al.]. by Robert Cook ... [et al.] by Robert M. Johnston ... [et al.]. by Roger S. Haydock ... [et al.] by Rune Elvik ... [et al.]. by R. Freiwillig ... [et al.]. by R. Glasfeld ... [et al.] by Robert C. Pooley ... by Robert Ewald Treybal.