Tarzan at the Earth's Core / Tarzan the Invincible

From Author Wars - https://authorwars.com/publications/tarzan-at-the-earths-core--tarzan-the-invincible-856680.html

Overview:

Title: Tarzan at the Earth's Core / Tarzan the Invincible
Author: Edgar Rice Burroughs
Year: Unknown
ISBN-10: 0345413490
Publisher: Del Rey / Ballantine
Price: $6.99
Binding: Paperback
Type: Omnibus
Title Reference: Tarzan the Invincible
Notes: Third printing per number line: 10 9 8 7 6 5 4 3. Source: Edgar Rice Burroughs: The Descriptive Bibliography of Ace and Ballantine / Del Rey Paperback Books (title, author, date, publisher, format, ISBN, price, printing, cover artist).