These are three volumes from the Nuts & Bolts series focusing on German military vehicles from WWII.

Volume 09 covers the 7,5 cm Pak 40/4 auf Raupenschlepper Ost (RSO).

Volume 12 details the Schwerer Zugkraftwagen 18 to (Famo "Bulle").

Volume 13 focuses on the Flakpanzer IV Wirbelwind and Ostwind