United States. War Department, Dictionary of Spoken Russian — §27… (1945)
“ A few verbs have a pr stem ending in consonant plus [y] ; these insert a vowel in the imv form: пить "to drink," пью, пьёт; the imv is пей, пейте. Some irregular verbs have the pr like Classes One, Two, and Three, but the pr stem ends in a consonant other than [n, j] : несу "I carry," несёшь, несёт, несём, несёте, несут, imv неси, несите. All those whose pr stem ends in [g] and nearly all whose pr stem ends in [k] replace these consonants by [ž] and [č] respectively before the endings that we write with [j] : могу "I can," можешь, может, можем, можете, могут, imv помоги "help" ”
