1. Royal Pain/Hollow Earth Affair
by Merwin, Richard & Spector, Warren 
Price: USD 2.00
Dealer: Alibris, Books N More Pa via Alibris
Description: TSR [ 3/1988] 1988 Paperback GOOD Paperback-9780880385510 TOP SECRET S.I. ADVENTURE [MERWIN, RICHARD & SPECTOR, WARREN] ROYAL PAIN/HOLLOW EARTH AFFAIR. 

2. The Hollow Earth Affair/The Royal Pain
by Richard Merwin Warren Spector 
Price: USD 14.36
Dealer: Biblio, Ergodebooks
Description: Wizards of the Coast, Date: 1988-04-01. Paperback. Used:Good. 1988. Wizards of the Coast ISBN 0880385510 9780880385510 [US]