Roman basilica vs basilica

Roman basilica

basilica

noun
  • A Christian church building having a nave with a semicircular apse, side aisles, a narthex and a clerestory. 

  • A Roman Catholic church or cathedral with basilican status, an honorific status granted by the pope to recognize its historical, architectural, or sacramental importance. 

How often have the words Roman basilica and basilica occurred in a corpus of books? (source: Google Ngram Viewer )