As similar datasets national bibliographies are not only about mapping the national traditions of publishing, but can also be studied comparatively and ultimately be integrated across borders should so that they help overcome a national perspective in analyzing the past. We have in this article expanded our previous pilot studies on the Finnish and Swedish bibliographies and the ESTC towards large-scale integration of national bibliographies in the CERL Heritage of the Printed Book Database. Our harmonization and integration efforts are not complete, but clearly demonstrate how such integration can help scholarship to reach a more precise view of print culture beyond the confines of national bibliographies.