If only one of parents held Byelorussian SSR citizenship then citizenship of the child was determined by joint declaration of his parents, without such a declaration child acquired citizenship of Byelorussian SSR by birth, given a right to follow citizenship of another parent upon becoming adult.
Citizenship of the child was determined by joint declaration of his parents. This was without such a declaration child. This such a declaration child was acquired citizenship of Byelorussian SSR by birth. This was given a right to follow citizenship of another parent upon becoming adult. Only one of parents held Byelorussian SSR citizenship then.