David Bawden Classification of chemical reactions: potential, possibilities and continuing relevance. 212-216 1991 31 Journal of Chemical Information and Computer Sciences 2 http://pubs.acs.org/cgi-bin/archive.cgi/jcisd8/1991/31/i02/f-pdf/f_ci00002a006.pdf db/journals/jcisd/jcisd31.html#Bawden91