  A convergent algorithm for nonnegative matrix factorization with
orthogonality constraints imposed on both factors is proposed in this paper.
This factorization concept was first introduced by Ding et al. with intent to
further improve clustering capability of NMF. However, as the original
algorithm was developed based on multiplicative update rules, the convergence
of the algorithm cannot be guaranteed. In this paper, we utilize the technique
presented in our previous work to develop the algorithm and prove that it
converges to a stationary point inside the solution space.
