Lambretta tail light lens screw for late series 2 and series 3 for CEV and Aprilia lenses only.
The Unofficial Lambretta Manual Update by Mark Haines
LAMBRETTA - ILLUSTRATED GUIDE TO THE IDENTIFICATION by Vittorio Tessera
Lambretta Performance Tuning and Conversions - 8099990
Lambretta Tuning Manual by Dave Webster - 8099992