The Brothers Hildebrandt
The brothers have been recognized artists in the world of Tolkien-inspired art. Other art includes the original poster art of Star Wars and over a hundred Marvel Masterpieces, including Swimsuit Specials.
 The Lord of the Rings
After seeing a Tolkien calendar with Tim Kirk's art, they responded to a call for artists by Ballantine. Their art was well-liked, and they were commissioned to illustrate the 1976 Ballantine calendar.
More calendars followed: 1977, 1978 - and they sold a record one million calendars. They moved their scope to other large projects, but kept producing Tolkien artwork. In 2001, Greg and Tim Hildebrandt: The Tolkien Years was published by Greg's son, Gregory Jr. Following the release of this collection, Ballantine began to reissue their popular Tolkien Calendars starting in 2002.
 Published artwork
- 1976 - Tolkien Calendar
- 1977 - Tolkien Calendar
- 1978 - Tolkien Calendar
- 1979 - The Art of the Brothers Hildebrandt
- 1985 - From Tolkien to Oz (by William McGuire)
- 2001 - Greg and Tim Hildebrandt: The Tolkien Years
- 2001 - J.R.R. Tolkien: Architect of Middle Earth (by Daniel Grotta)
- 2002 - Tolkien Calendar
- 2003 - Postcard Calendar
- 2004 - Tolkien Calendar
- 2005 - Tolkien Calendar
- 2005 - Tolkien Calendar (mini)
- 2006 - Tolkien Calendar.