This link enables one to download the 54 page introductory section of the CINDAS book (9.5 MB pdf), Thermophysical Properties of Matter, Vol. 7 Edited by Y.S. Touloukian and D.P. DeWitt IFC/Plenum -1970. It contains some excellent details on the meaning of emissivity, its terminology, the measurement techniques of 1970 and an introduction to the data organization of the full volume.