English language usage and style guides which have entries for "acronym" generally criticize the usage that refers to forms that are not pronounceable words. "Fowler's Dictionary of Modern English Usage" says that "acronym" "denotes abbreviations formed from initial letters of other words and pronounced as a single word, such as "NATO" (as distinct from "B-B-C")" but adds later "In everyday use, "acronym" is often applied to abbreviations that are technically initialisms, since they are pronounced as separate letters." The Chicago Manual of Style acknowledges the complexity ("Furthermore, an acronym and initialism are occasionally combined (JPEG), and the line between initialism and acronym is not always clear") but still defines the terms as mutually exclusive. Other guides outright deny any legitimacy to the usage: "Bryson's Dictionary of Troublesome Words" says "Abbreviations that are not pronounced as words (IBM, ABC, NFL) are not acronyms; they are just abbreviations." "Garner's Modern American Usage" says "An acronym is made from the first letters or parts of a compound term. It's read or spoken as a single word, not letter by letter." "The New York Times Manual of Style and Usage" says "Unless pronounced as a word, an abbreviation is not an acronym."