We give a new algorithm to construct optimal alphabetic ternary trees, where every internal node has at most three children. This algorithm generalizes the classic Hu-Tucker algorithm, though the overall computational complexity has yet to be determined.
@article{arxiv.1402.3036,
title = {Optimal Alphabetic Ternary Trees},
author = {J. David Morgenthaler and T. C. Hu},
journal= {arXiv preprint arXiv:1402.3036},
year = {2014}
}