STUTTGART, Germany 6 March 2020: The Porsche-Diesel Schlepper “Standard 218”, the third generation of the two-cylinder Standard tractor series. The Po Stock Photo - Alamy
Porsche Standard T 217 – Wikipedia
Traktorenlexikon: Porsche-Diesel – Wikibooks, Sammlung freier Lehr-, Sach- und Fachbücher