Abbott, D. H.; Biscaye, P.; Cole-Dai, J.; Breger, D.; Biscaye; Cole-Dai; Breger (December 2008). «Magnetite and Silicate Spherules from the GISP2 Core at the 536 A.D. Horizon». AGU Fall Meeting Abstracts41: 1454. Abstract #PP41B-1454. Bibcode: 2008AGUFMPP41B1454A.