↑ Bigelow, Charles (1986). "Notes on Typeface Protection" (PDF). TUGboat. 7 (3): 146–151. สืบค้นเมื่อ 27 December 2018. IBM neglected to trademark the typeface names like Courier and Prestige, so once the patents had lapsed, the names gradually fell into the public domain without IBM doing anything about it (at the time, and for a dozen years or so, IBM was distracted by a major U.S. anti-trust suit). Most students of the type protection field believe that those names are probably unprotectable by now, though IBM could still presumably make a try for it if sufficiently motivated.
