THE SIGNS OF WHICH TIMES? CHRONOLOGICAL AND PALAEOENVIRONMENTAL ISSUES IN THE ROCK ART OF NORTHERN AFRICA THE SIGNS OF WHICH TIMES? CHRONOLOGICAL AND PALAEOENVIRONMENTAL ISSUES IN THE ROCK ART OF NORTHERN AFRICA Guest Editors: D. HUyGE, F. VAN NOTEN & D. SWINNE 2012 ROYAL ACADEMY FOR OVERSEAS SCIENCES