Lewis, D. (1984). Pencil drawing techniques. Watson-Guptill Publications.
芝加哥风格引文Lewis, David. Pencil Drawing Techniques. New York: Watson-Guptill Publications, 1984.
MLA引文Lewis, David. Pencil Drawing Techniques. Watson-Guptill Publications, 1984.
警告：这些引文格式不一定是100％准确.