RT Journal Article SR Electronic T1 Science's Top 20 Greatest Hits JF Science JO Science FD American Association for the Advancement of Science SP 267 OP 267 DO 10.1126/science.251.4991.267 VO 251 IS 4991 A1 P., R. YR 1991 UL http://science.sciencemag.org/content/251/4991/267.abstract AB