Entire series- Paul Christopher's Finn Ryan books

All 4 books of Paul Christopher's Finn Ryan series, with archaeology action/adventures staring a woman. They were my husband's. As shown in the photos, all of them show signs of wear, but are in mostly decent condition. Aztec Heresy has some yellow on the bottom page edges, and Michelangelo's Notebook and Lucifers Gospel have some small damage to the covers.