The early version of the fugue (BWV 902/2, 60 bars long) is found in several sources, and known in two slightly different versions.
The earlier version is transmitted to Vogler's MS P 1089
and others ,
while the later version is transmitted to Kellner's MS P 804 alone
.
No autograph survives. The 'London autograph' is a copy made by Anna
Magdalena. There are no significant differences between two manuscript
traditions .