A very high quality Lambretta GP flywheel nut and washer by MB Scooters in the UK.
MBL1281K INNOCENTI 22017024 Flywheel Nut 83100012 Wave Washer
The Complete Spanner's Manual: Lambretta Scooters by Martin 'Sticky' Round Third Edition 8100072
The Complete Spanner's Lambretta Kit Book
Eibar Lambrettas 1954-1989 by Jaime de Prat Salomone
The Unofficial Lambretta Manual Update by Mark Haines