APA

United States, . (1981). Solar collectors: what they are and how they operate. [Washington, D.C.]: .

Chicago

United States, . 1981. Solar collectors: what they are and how they operate. [Washington, D.C.]: .

Harvard

United States, . (1981). Solar collectors: what they are and how they operate. [Washington, D.C.]: .

MLA

United States, . Solar collectors: what they are and how they operate. [Washington, D.C.]: . 1981.