Girdler Jr., Reynolds (1967). "Crayons in the History of the Arts". Art Education. 20 (1). National Art Education Association: 31–32. doi:10.2307/3190944. JSTOR3190944.
Girdler Jr., Reynolds (1967). "Crayons in the History of the Arts". Art Education. 20 (1). National Art Education Association: 31–32. doi:10.2307/3190944. JSTOR3190944.