@article{700067,
     title = {Application of the Ritz method to the solution of parabolic boundary value problems of arbitrary order in the space variables},
     booktitle = {Proceedings of Equadiff III},
     series = {GDML\_Books},
     publisher = {Univ. J. E. Purkyn\v e - P\v r\'\i rodov\v edeck\'a fakulta},
     address = {Brno},
     year = {1973},
     pages = {255-260},
     mrnumber = {MR0347111},
     zbl = {0324.65049},
     url = {http://dml.mathdoc.fr/item/700067}
}

Rektorys, Karel. Application of the Ritz method to the solution of parabolic boundary value problems of arbitrary order in the space variables, dans Proceedings of Equadiff III, GDML_Books,  (1973), pp. 255-260. http://gdmltest.u-ga.fr/item/700067/