On the state complexity of intersection of regular languages. - Sheng Yu 001; Qingyu Zhuang (SIGACT News, 1991)

Obtaining Tight Upper Bounds for the State Complexities of DFA Operations. - Sheng Yu 001; Qingyu Zhuang; Kai Salomaa (ICCI, 1992)

The State Complexities of Some Basic Operations on Regular Languages. - Sheng Yu 001; Qingyu Zhuang; Kai Salomaa (Theor. Comput. Sci., 1994)