B. DasGupta, X. He, T. Jiang, M. Li, J. Tromp, and L. Zhang. Discrete Mathematical Problems with Medical Applications, volume 55 of DIMACS Series in Discrete Mathematics and Theoretical Computer Science, page 125-143. DIMACS/AMS, (1999)
M. Li, and P. Vitányi. Language Computations, volume 17 of DIMACS Series in Discrete Mathematics and Theoretical Computer Science, page 127-148. DIMACS/AMS, (1992)