The main result of the paper is
the inequality (11),
which is called now Mandelshtam-Tamm inequality.
This fundamental inequality is a special case of
the certainty principle,
applied to the quantum evolution in the Schrödinger representation.
References
Л. И. Мандельштам, И. Е. Тамм „Соотношение неопределённости
энергия-время в нерелятивистской квантовой механике”,
Изв. Акад. Наук СССР (сер. физ.) 9, 122-128 (1945).
[original Russian version]
L. I. Mandelshtam, I. E. Tamm “The uncertainty relation
between energy and time in nonrelativistic quantum
mechanics”, J. Phys. (USSR) 9, 249-254 (1945).
[English version]
Л. И. Мандельштам, Полное собрание трудов
2, 306-315, М.-Л. (1947).
[another Russian version]
If you have access to the original Russian version, and you are ready to scan it, please, let me know.