The Asser series is the most important source of civil law in the Netherlands. The complete Asser series (+30 volumes) is now available in book form in Law Library Limburg, but can also be consulted online in Kluwer Navigator via Maastricht University.
To log in on Kluwer Navigator: click on "inloggen via WO/HBO", choose Maastricht University and log in with your UM credentials. Next click on "uitgaven" and then on "Asser-serie".