United States. War Department

“ DECLENSION OF NOUNS
First Declension. Nouns of the First Declension have the following endings. Our example shows the stem [yam-] "pit."
The is has also a longer form in [-oyu] : ямою, рукою or рукой.
Most nouns of this declension are F. A few, denoting persons, are M: судья "judge." All those that denote only male persons are M: дядя "uncle." A few that denote persons are M or F, according to the sex: сирота "orphan": этот сирота "this (male) orphan," эта сирота "this (female) orphan." ”

“ Two nouns, [matj'rj-] "mother" and [doč'rj-] "daughter," drop the last syllable in the ns: мать, gdls матери, is матерью.
The few N nouns drop the last syllable and take the ending [-a] in the ns: [imjonj-] "name," ns имя, gdls имени; they have is [-om] : именем, and a P stem with hard [n] and stress on the endings: np имена, gp имён, dp именам; similarly the old-fashioned word дитя "child," gdls дитяти, is дитятею, no P forms. ”

“ Note that the ns ending when unstressed sounds like the gs and np: [bljuda] ; the difference appears under stress: окно "window," gs окна. Similarly after soft consonants: ns поле "field" [polja] sounds just like gs поля, but ns ружьё [ružyo] "gun" differs from gsружья [-žya] . ”