Initially thirteen chapters were planned, but only the first four (making a total of approximately 1500 pages) were published. Much of the material which would have been found in the following chapters can be found, in a less polished form, in the "Séminaire de géométrie algébrique" (known as "SGA"). Indeed, as explained by Grothendieck in the preface of the published version of "SGA", by 1970 it had become clear that incorporating all of the planned material in "EGA" would require significant changes in the earlier chapters already published, and that therefore the prospects of completing "EGA" in the near term were limited. An obvious example is provided by derived categories, which became an indispensable tool in the later "SGA" volumes, but was not yet used in "EGA III" as the theory was not yet developed at the time. Considerable effort was therefore spent to bring the published "SGA" volumes to a high degree of completeness and rigour. Before work on the treatise was abandoned, there were plans in 1966–67 to expand the group of authors to include Grothendieck's students Pierre Deligne and Michel Raynaud, as evidenced by published correspondence between Grothendieck and David Mumford. Grothendieck's letter of 4 November 1966 to Mumford also indicates that the second-edition revised structure was in place by that time, with Chapter VIII already intended to cover the Picard scheme. In that letter he estimated that at the pace of writing up to that point, the following four chapters (V to VIII) would have taken eight years to complete, indicating an intended length comparable to the first four chapters, which had been in preparation for about eight years at the time.