Check out this multi-page web exhibit by Gareth Cordery, a student of Susan Boynton at Columbia University: http://liturgicalmanuscripts.sandbox.library.columbia.edu/barnardbarlines/. Close-up photos and explanations of the varied scribal uses of vertical lines in the manuscript New York, Columbia University - Barnard College Library, MS 1 are accompanied by an extensive bibliography and comparative statistical analysis. The glossary of terms and links to other web resources are certain to be helpful for students, too!

Barnard MS1 is indexed in the Cantus Database: https://cantusdatabase.org/source/683940.