About the origin:

Many sources have survived on Bartók's "Mikrokosmos", in which the origins of this highly interesting collection - from the first drafts to the copies used by Bartók in concert and the first edition - can be traced. The Critical Commentary, published in a separate volume of the Complete Edition, therefore contains not only a description of the sources and the readings of the edition, but also an extensive chapter entitled "The Compositional Process", in which the genesis is described in detail for the first time, based on the sources in numerous diplomatic transcriptions.

About further sources and explanations:

In the appendix to the volume, transcriptions of Bartók's own recordings as well as earlier versions are presented for some of the pieces. In addition, Bartók's later explanations of his work to his student Ann Chenée are documented.