%0 Journal Article %A L. L. Pitaevskaya %A B. E. Kanishchev %T Ultrasound propagation velocity in nitrogen -- methane mixtures under pressures up to $4$ kbars %J Doklady Akademii Nauk %D 1976 %P 1345-1346 %V 229 %N 6 %I mathdoc %U http://geodesic.mathdoc.fr/item/DAN_1976_229_6_a17/ %G ru %F DAN_1976_229_6_a17