Twice Q-polynomial distance-regular graphs are thin. - Garth A. Dickie (Eur. J. Comb., 1995)

Dual Bipartite Q-polynomial Distance-regular Graphs. - Garth A. Dickie; Paul M. Terwilliger (Eur. J. Comb., 1996)

Twice Q-Polynomial Distance-Regular Graphs. - Garth A. Dickie (J. Comb. Theory, Ser. B, 1996)