National bibliographies can provide comprehensive quantitative insights to the overall historical dynamics of the evolving publishing landscape across time and geography. Biases in data collection or quality may remarkably hinder productive research use of the bibliographies, however. Drawing valid conclusions critically depends on efficient and reliable harmonization and augmentation of the raw entries. In our study based on the Swedish National Bibliography and the Finnish National Bibliography and focusing on publication patterns in Sweden and Finland during the period 1640-1910, we have encountered specific and largely overlooked challenges in using bibliographic catalogues for historical research. Here, we have demonstrated how such challenges can be overcome by specifically tailored open source workflows for data processing and analysis. Furthermore, we show how external sources of metadata, for instance, on authors, publishers, or geographical places, can be used to enrich and verify bibliographic information. This work has potential for wider implementation in related studies and other bibliographies, and provides guidelines for more extensive integration of national catalogues, thus helping to overcome the national view in analysing the past towards a more precise view of print culture beyond the confines of national bibliographies.
In addition, we are now releasing a notably improved version of the Finnish national bibliography FNB. 
We discuss the future implications of these methods.