1. Lomanitz, U. S. Patent 1,244,521 (1918).
2. Gardner and Holdt, Pt. Manu. Assoc. of U. S. Circ. No. 105, Oct. 1920.
3. Gardner, Pt. Manu. Assoc. of U. S. Circ. No. 257, 216–27 (1936).
4. Gardner, Am. Paint J.22, Conv. Daily 7–8 (1937).
5. Stewart, Drugs, Oils and Paints52, 404–5 (1937).