Smith, Robert Ross (1953). The Approach to the Philippines. The United States Army in World War II. Washington, D.C.: United States Army Center of Military History. pp. 53–83. OCLC570739529.
Laycock, Donald C. (1965). The Ndu language family (Sepik District, New Guinea). Canberra: Australian National University. OCLC 810186.
search.worldcat.org
Smith, Robert Ross (1953). The Approach to the Philippines. The United States Army in World War II. Washington, D.C.: United States Army Center of Military History. pp. 53–83. OCLC570739529.