Bao Qinglan; Sun Jiong; Hao Xiaoling; Zettl Anton: Characterization of self-adjoint domains for regular even order C-symmetric differential operators. (2019)
Hao Xiaoling; Zhang Maozhu; Sun Jiong; Zettl Anton: Characterization of domains of self-adjoint ordinary differential operators of any order even or odd. ISBN 1417 3875, (2017)