@article{TMF_1974_18_2_a14,
     author = {R. R. Nigmatullin},
     title = {A~method for calculating time correlation functions},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {286--295},
     year = {1974},
     volume = {18},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1974_18_2_a14/}
}