Complex sentence: Palladio was undoubtedly the designer of another (incomplete) Villa Trissino some 20 km away at Sarego, as documented by his published plan in "I quattro libri dell'architettura" ("The Four Books of Architecture").
Split into simpler sentences: Palladio was undoubtedly the designer of another (incomplete) Villa Trissino some 20 km away at Sarego. Palladio published the plan in "I quattro libri dell'architettura" ("The Four Books of Architecture").