 Some contemporary authorities such as the Associated Press Stylebook recommend or allow the practice of omitting the additional "s" in all words ending with an "s", but not in words ending with other sibilants ("z" and "x").The 15th edition of "The Chicago Manual of Style" had recommended the traditional practice, which included providing for several exceptions to accommodate spoken usage such as the omission of the extra "s" after a polysyllabic word ending in a sibilant, but the 16th edition no longer recommends omitting the possessive "s".Similar examples of notable names ending in an "s" that are often given a possessive apostrophe with no additional "s" include "Dickens" and "Williams".