Pinsker's original paper is now available online in the archive of the International Teletraffic Congress: http://ww.i-teletraffic.org/fileadmin/ITCBibDatabase/1973/pinsker731.pdf

Pinsker's original paper is now available online in the archive of the International Teletraffic Congress: https://itc-conference.org/itc-library/itc07.html

Pinsker, Mark S. On the Complexity of a Concentrator. 7th International Teletraffic Congress, pp. 318/1-318/4, 1973