@article{DM_1992_4_2_a7,
     author = {G. I. Kalmykov},
     title = {Partial ordering of trees and the classification of connected graphs and blocks},
     journal = {Diskretnaya Matematika},
     pages = {66--73},
     year = {1992},
     volume = {4},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_1992_4_2_a7/}
}