&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Bulletin of Mathematical Biology. 1973.<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Vol. 35 No. 1/2 : Vol. 35 No. 1/2. &mdash; 1973. &mdash; ISSN 0092-8240.<br><br><br><br>[ SYS NUM: 15398 ]