On q-trees. - Chong-Yun Chao; Nian-Zu Li; Shao-Ji Xu (J. Graph Theory, 1986)

Classification of chromatically unique graphs having quadratic σ-polynomials. - Nian-Zu Li; Earl Glen Whitehead Jr.; Shao-Ji Xu (J. Graph Theory, 1987)

On graphs having sigma-polynomials of the same degree. - Nian-Zu Li (Discret. Math., 1992)

The chromatic uniqueness of W10. - Nian-Zu Li; Earl Glen Whitehead Jr. (Discret. Math., 1992)

The chromaticity of certain graphs with five triangles. - Nian-Zu Li; Earl Glen Whitehead Jr. (Discret. Math., 1993)

On q-graphs. - Chong-Yun Chao; Zhi-Yi Guo; Nian-Zu Li (Discret. Math., 1997)