Four-Day Planet / Lone Star Planet

From Author Wars - https://authorwars.com/publications/four-day-planet--lone-star-planet-14483.html

Overview:

Title: Four-Day Planet / Lone Star Planet
Author: H. Beam Piper, John J. McGuire
Year: 1979
ISBN-10: 044124890X
Publisher: Ace Books
Price: $2.25
Pages: 340
Binding: Paperback
Type: Omnibus
Title Reference: Four-Day Planet
Notes:
- "First Ace printing: April 1979"; no number line
- Cover art by Michael Whelan on copyright page, the artwork is also 'signed'
- The only author credited on the cover is H. Beam Piper.
- None of the three title pages (one for the omnibus and two for the constituent novels) lists the authors, but every even-numbered page of ''Four-Day Planet'' says "H. Beam Piper" at the top and every even-numbered page of ''Lone Star Planet'' says "H. Beam Piper and John J. McGuire" at the top.