Lambretta tail light lens screw for series 1 and early series 2Two are required to hold the lens in place.
The Complete Spanner's Manual: Lambretta Scooters by Martin 'Sticky' Round Third Edition 8100072
The Complete Spanner's Lambretta Kit Book 8100027T
Eibar Lambrettas 1954-1989 by Jaime de Prat Salomone
Lambretta and Vespa Street Racers BOOKAZINE by Stuart Owen