Author,Title,Edition,Publisher,Year,Series,Number,ISBN,ISSN,URL
"Bobylev, Nikolai A. and Emelʹi︠a︡nov, Stanislav Vasilʹevich and Korovin, Sergey K. and Vakhrameev, S. A.",Geometrical methods in variational problems,,Kluwer Academic,1999,Mathematics and its applications,,0792357809,,https://cir.nii.ac.jp/crid/1130282272848020992