Application of Lyapunov's direct method to the error-propagation effect in convolutional codes (Corresp.). - James L. Massey; R. W. Liu (IEEE Trans. Inf. Theory, 1964)

Analysis of the Generalized Stochastic Petri Nets by State Aggregation. - Hany H. Ammar; R. W. Liu (PNPM, 1985)