@article{VMP_2003_4_1_a15,
     author = {O. I. Berngardt and A. L. Voronov},
     title = {A least squares method for sums of functions satisfying the differential},
     journal = {Numerical methods and programming},
     pages = {167--171},
     year = {2003},
     volume = {4},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMP_2003_4_1_a15/}
}