&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Bulletin of Mathematical Biology. 1973.<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Vol. 35 No. 5/6 : Vol. 35 No. 5/6. &mdash; 1973. &mdash; ISSN 0092-8240.<br><br><br><br>[ SYS NUM: 15401 ]