Fazzioli, Edoardo. Chinese calligraphy : from pictograph to ideogram : the history of 214 essential Chinese/Japanese characters. calligraphy by Rebecca Hon Ko. New York: Abbeville Press. ISBN0-89659-774-1.
^Depending on the fonts installed on your computer, these characters may or may not be displayed correctly on your browser. The 龜 character has minor visual differences between the official typefaces used in Japan, based on the Kangxi Dictionary, and Korea, Taiwan (ROC) and China (PRC). For the China variant, there are no stroke crossings across the "body" of the turtle; drawing the head would follow a similar stroke order pattern to writing "口", with all upper edges being completed before the box is closed at the bottom. As for the variants in Korea, Taiwan and as listed in the Kangxi Dictionary, strokes do cross over the turtle "body", however in different places and in different manners; for the Korea variant, lines over the body only cross vertically at the head, forming two 口 "boxes" where one "overlaps" another, namely the "body" part; for the Kangxi variant, there is the vertical crossing as with the Korea variant, however there are also horizontal crossings over the body so that the "arms" of the turtle joins with the "shell" at the back, rather than the front of the body; the Taiwan variant is similar to the Kangxi variant, only there is a missing line that no longer joins the "shell" with the "tail" of the turtle. The Kangxi, Korea and Taiwan variants all involve a flicked curve at the top of the head, similar in "鱼", whereas the China variant simply has a dot. For the China radical, the "arms" are separate from the "body", and as with the Korea radical, do not have lines which cross the "body". Each variant also employs different types of brush flicks for the tail and the "cross" on the "shell", with each varying in size and direction. The varying thickness of each typeface on some browsers is simply due to the installed font, and does not represent any actual difference in line thickness between the variant characters; hypothetically, each character should have the same line thickness.