1. Ueber eine neue Methode zur Lösung gewisser Variationsprobleme der mathematischen Physik;Ritz;J Reine Angew Math,1908
2. Mathematical theory of elasticity;Sokolnikoff,1956
3. Filippov VM. Construction of extremal variational principles in non-Euler functional classes for PDE's of second order with nonpotential operators. физика элементарных Частицб, и атомново Ядра 31 вып 7а 2000;9:5–96.
4. The analog equation method. A powerful BEM-based solution technique for solving linear and nonlinear engineering problems;Katsikadelis,1994
5. The analog equation method. A boundary-only integral equation method for nonlinear static and dynamic problems in general bodies;Katsikadelis;Theor Appl Mech,2002