. "107515011"@en-us . "105991626"@en-us . "direct sum"^^ . . "direct sum"@en-us . . "107998904"^^ . . . . . "a union of two disjoint sets in which every element is the sum of an element from each of the disjoint sets"@en-us . . "0"^^ . . "0"^^ . "07998904-n"^^ .