sentences:  "Cool Then, Cool Now," a two-CD/book released on Hip-O Records in 2011, examined the artist's signature hits along with a significant dose of lesser-known recordings.It is believed that Martin's worldwide record sales exceed 50 million units.Since many radio stations in the US adopt a format change to Christmas music each December, many holiday hits have an annual spike in popularity during the last few weeks of the year and are retired once the season is over.