@article{ZNSL_1990_182_a1,
     author = {N. M. Ivochkina},
     title = {Minimization of the functionals generating curvature operators},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {29--37},
     year = {1990},
     volume = {182},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1990_182_a1/}
}