Kent, William H. “Catholic Encyclopedia (1913)/Indulgences”. 위키인용집 (영어). 2019년 5월 20일에 확인함. This entry on indulgences suggests that the evolution of the doctrine came to include pilgrimage to shrines as a trend that developed from the 8th century A.D.: "Among other forms of commutation were pilgrimages to well-known shrines such as that at St. Albans in England or at Compostela in Spain. But the most important place of pilgrimage was Rome. According to Bede (674–735) the visitatio liminum, or visit to the tomb of the Apostles, was even then regarded as a good work of great efficacy (Hist. Eccl., IV, 23). At first the pilgrims came simply to venerate the relics of the Apostles and martyrs; but in course of time their chief purpose was to gain the indulgences granted by the pope and attached especially to the Stations."
