Following the enthusiastic reception of the two volumes of January, Bolland and Henschenius started preparing the month of February, which appeared in three volumes in 1658; March (1668) and April (1675) followed, each in three volumes. The publication of May, in seven volumes plus a special volume dedicated to the chronology of the popes (1680-88), reflects a huge increase in the materials published. The main reason for this was a journey of two and a half years to Rome via Germany, Italy and France undertaken by Henschenius and a new collaborator, Daniel Van Papenbroek (Papebrochius). Between July 1660 and December 1662 the two Jesuits visited monasteries, convents, cathedrals and castles, explored their libraries, examined their hagiographic manuscripts and copied innumerable Greek and Latin texts, which complemented Rosweyde's collection in Antwerp. From that moment 'literary travels' would become traditional, not only for Bolland's successors but also for other groups dedicated to erudition such as the Maurist Benedictine monks. If such travels made it possible to collect numerous texts at random, some of which would be published more than a century later, the preparation of a volume of the Acta Sanctorum often revealed the lack of some specific documents, which our hagiographers would try to obtain by writing to local scholars. A huge correspondence was thus exchanged between Antwerp and scholars all over Europe.