1. J.W. Calkin, Abstract symmetric boundary conditions. Trans. Am. Math. Soc. 45(3), 369–442 (1939)
2. J. Delsarte, Sur une extension de la formule de taylor. J. Math. Pure Appl. XVII(3), 213–231 (1938)
3. H. Emamirad, A. Rougirel, Abstract differential triplet and boundary restriction operators with application to fractional differential operators (2021). Preprint. https://hal.archives-ouvertes.fr/view/index/docid/3200134
4. H. Emamirad , A. Rougirel, Delsarte equation for Caputo operator of fractional calculus. Fract. Calc. Appl. Anal. 25(2), 584–607 (2022)
5. V. Ryzhov, A general boundary value problem and its Weyl function. Opuscula Math. 27(2), 305–331 (2007)