They may also try to work "clean" either because they prefer doing so or because they wish to reach audiences that disdain raunchy material. Among those who do so as a preference are Brian Regan, Bob Newhart, and Bill Cosby. Ray Romano is capable or even willing to work "blue," as demonstrated on "Dr. Katz, Professional Therapist" DVD commentary tracks, but has tended to avoid doing so out of deference to his current audience. Note: An attempt has been made to avoid repeating names already mentioned, but some repetition might still exist. This list is partial and mostly deals with American comedians or humorists who won Lifetime Achievement awards in their fields or were placed in lists of history's great comedians.