Nonclassical Sturm-Liouville problems and Schrödinger operators on radial trees. Carlson, Robert — 2000 Electronic Journal of Differential Equations (EJDE) [electronic only]
Hill's equation for a homogeneous tree. Carlson, Robert — 1997 Electronic Journal of Differential Equations (EJDE) [electronic only]
Adjoint and self-adjoint differential operators on graphs. Carlson, Robert — 1998 Electronic Journal of Differential Equations (EJDE) [electronic only]
Ambarzumian's theorem for trees. Carlson, Robert; Pivovarchik, Vyacheslav — 2007 Electronic Journal of Differential Equations (EJDE) [electronic only]
Grassmannian subvarieties arising in the spectral theory of ordinary differential operators. Robert Varley; Robert Carlson — 1980 Journal für die reine und angewandte Mathematik