@article{MO_2015_1_a4,
     author = {E. N. Petrova and S. A. Pirogov},
     title = {Different addition of different quantities},
     journal = {Matemati\v{c}eskoe obrazovanie},
     pages = {53--55},
     year = {2015},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MO_2015_1_a4/}
}