This work contains Iceland's three computistical treatises. Edited by Kålund, with a long introduction on medieval time-reckoning by Beckman. WARNING: This 600-dpi reprint, though well legible, is not identical in quality to the original edition. Judge the quality of the scan for yourself at septentrionalia.net before purchase. (This is the hardcover edition of this book, which is also available in paperback.)