Vasiliy Lebedev-Kumach, whose "Pesnya o Tsusime" ("Tsushima Song") is heard in the movie died in 1949, in which main events of the movie unfold.
Blind veteran (Yakov Stepanov dubbed by an uncredited Avangard Leontev) is unaware of song Nemchinov sings, "Vragi sozhgli rodnuyu khatu", as it was banned shortly after being published in 1946.
Title of Sergei's dissertation, "Features of space organization of bio-electrical brain activity during speech" is real and is from a 1985 dissertation by Lidiya Shustova. Writer Nadezhda Kozhushanaya wrote it down for later use when she was working as a typist for dissertation and was impressed by it.