At the Earth's Core

From Author Wars - https://authorwars.com/publications/at-the-earths-core-248473.html

Overview:

Title: At the Earth's Core
Author: Edgar Rice Burroughs
Year: Unknown
Publisher: Ace Books
Price: $0.95
Pages: 159
Binding: Paperback
Type: Novel
Title Reference: At the Earth's Core
Notes: Artist not credited, http://www.erbzine.com/mag7/0741.html says Frazetta, looks like his style. No printing date given. Robert B. Zeuschner's Edgar Rice Burroughs: The Bibliography confirms the Frazetta cover and also indicates that this fifth Ace printing was published in 1972 or 1973.