Volume 31 of the Technical Bulletin contains the following essays:
•In Search of Verrocchio, Painter and Master: The Virgin and Child with Two Angels
•Giorgione and not Giorgione: The Conservation History and Technical Examination of Il Tramonto
•The Virgin and Child with an Angel, after Francia: A History of Error
•Two Copies of Perugino's Baptism of Christ
•Rembrandt's Portrait(s?) of Frederik Rihel
•Mastic and Megilp in Reynold's Lord Heathfield of Gibraltar: A Challenge for Conservation
http://www.nationalgallery.co.uk/shop/search/national_gallery_technical_bulletin/1018117