In 2016, we made a preliminary survey on the systematic comparison of Uses regarding the Divine Office. Although the world-famous Cantus Database has provided an excellent research tool for decades, its selection of sources and geographical scope is rather arbitrary. Therefore, its results can often be misleading, at least in terms of statistical relevance. The first step to introduce the methodology of Usuarium was the processing of the Psalters from 38 printed Breviaries throughout Europe. As weekday offices were not very frequently recited in the Middle Ages, they formed a practically intact layer within the Divine Office. As such, they are the most reliable witnesses of the basic variation of the Divine Office before its specific local divergences in the Sanctoral and even the Temporal part. The first conclusions of the survey were formulated in an unpublished study with the title 'Interpreting Latin Liturgical Psalters'. Recently, the underlying material has also been uploaded and can be consulted either via the concerning Breviaries or comprehensively by selecting the filter for the 'Psalter' part.