Task: Sentence Expansion
Input (English): From 1921 to 1944 , Tuva was a separate country called Tannu-Tuva .
Output (English): From 1921 to 1944 , Tuva constituted a sovereign , independent nation under the name of Tannu Tuva , officially , the Tuvan People 's Republic , or the People 's Republic of Tannu Tuva .