This four-volume work represents the most comprehensive documentation and study of the creation of general relativity. Einstein¿s 1912 Zurich notebook is published for the first time in facsimile and transcript and commented on by today¿s major historians of science. Additional sources from Einstein and others, who from the late 19th to the early 20th century contributed to this monumental development, are presented here in translation for the first time. The volumes offer detailed commentaries and analyses of these sources that are based on a close reading of these documents supplemented by interpretations by the leading historians of relativity.