Columbia subject headings:
Rome (Italy)--Buildings, structures, etc.
San Gregorio al Celio (Abbey : Rome, Italy)
Harvard subject headings:
Rome (Italy)--Buildings, structures, etc.
San Gregorio al Celio (Abbey : Rome, Italy)
Princeton subject headings:
Rome (Italy)--Buildings, structures, etc.
San Gregorio al Celio (Church : Rome, Italy)--History.