Issue No. 02 - February (1978 vol. 27)
A. Wetjen , Zeppelinstrasse
Clustering may be viewed as a combinatorial optimization problem. In the above paper<sup>1</sup>, the number of ways in which N objects may be assigned to M distinct classes is given by One can easily see that this can be true if and only if M! is a divisor of MN and this is true if and only if M = 1 or M = 2.
A. Wetjen, "Comments on "A Branch and Bound Clustering Algorithm"", IEEE Transactions on Computers, vol. 27, no. , pp. 189, February 1978, doi:10.1109/TC.1978.1675059