Fixing the focus to infinity issue of the Helios 44-2 on M42 to Nikon F mount adapter - YouTube
Helios 44/2 on Nikon F mount infinity focus achieved without extra glass adapter | Nikon DSLR and M42 lenses (all Nikon DSLR from 2006 onwards) | Flickr
Mod: Autofocus Helios-44 for Nikon pt2 | Richard Haw's Classic Nikon Repair and Review
MC HELIOS-44M-4 58mm 1:2 lens information and sample photos - Nikon Rumors