Throughout the Middle Ages people travelled to the Holy Land in very large numbers. The men - women were very few and far between - that travelled to what was felt to be the centre of the world may have been motivated by vastly differing aims, but they all faced the same perilous (and costly) journey. Travelling was hard work as roads were often in bad repairs, rivers had to be crossed while there were not many bridges and ferries, and there were hardly any signposts. Only the rich could afford horses and those that could not had to go on foot. The transport of pilgrims over the Mediterranean was taken care of chiefly by the Venetians. The crossing wasn't fun either: pilgrims complain about the noise, rats, seasickness, hunger, thirst, food that was infested with maggots, water that stank and boredom. As soons as the pilgrims disembarked Franciscan friars came to the rescue. They were the 'principalle resort and help' for all pelgrims and showed them all the holy places and explained, in different languages, what had to be known. The whole tour of the country, including a visit to holy places outside Jerusalem, seems to have been completed in about ten days only. We know how one travelled and what one endured because hundreds of pilgrims wrote about their journey. Many of those late mediaeval texts post dating 1300 show striking similarities: over and over again, the same places in the Holy Land are mentioned in much the same words and often in the same order. This phenomenon has repeatedly been put down to the use of a common source: some sort of Guide Michelin for pilgrims that could be obtained from the Franciscan friars. Josephie Brefeld is first to succeed in proving the existence of this source-text and she even shows us what it looked like. In doing so she used a statistical method widely used in the social sciences but hardly ever before in the study of texts. Factor analysis is a method for sorting out relations between variables if there is a large amount of data. Data on relevant variables are collected - in this case the holy places mentioned in a corpus of 18 pilgrimage texts - and entered into a matrix, correlation coefficients between the variables are calculated and on the basis of these coefficients factors are extracted. One of the factors, Brefeld convincingly argues, is the influence of a written source-text. Textual arguments support her findings. Brefeld is also able to pin down a cluster of closely related source-texts. One of them is presented in her book. Because of her lucid explanation of the methods she used Brefelds study is an important methodological step forward in the field of textual criticism.