"6". German explosive ordnance. OP 1666. Vol. 2. United States Navy Bureau of Ordnance. 1947. p. 607. OCLC505967055.
Bethell (1911), p. 96. Bethell, H. A. (1911). Modern artillery in the Field: A Description of the Artillery of the Field Army, and the Principles and Methods of its Employment. London: Macmillan & Co. OCLC4533477.
Bethell 1911, p. 95. Bethell, H. A. (1911). Modern artillery in the Field: A Description of the Artillery of the Field Army, and the Principles and Methods of its Employment. London: Macmillan & Co. OCLC4533477.