Columbia subject headings:
Fortification--Italy--Perugia--Guidebooks.
Fortification--Italy--Perugia--Pictorial works.
Paolina Fort (Perugia, Italy)--Guidebooks.
Paolina Fort (Perugia, Italy)--Pictorial works.
Perugia (Italy)--Buildings, structures, etc.--Guidebooks.
Perugia (Italy)--Buildings, structures, etc.--Pictorial works.
Harvard subject headings:
Fortification--Italy--Perugia--Guidebooks.
Fortification--Italy--Perugia--Pictorial works.
Paolina Fort (Perugia, Italy)--Guidebooks.
Paolina Fort (Perugia, Italy)--Pictorial works.
Perugia (Italy)--Buildings, structures, etc.--Guidebooks.
Perugia (Italy)--Buildings, structures, etc.--Pictorial works.
Princeton subject headings: