Diplomatarium Norvegicum (DN) is one of the defining collections of source material from Norway's medieval period.  Its 22 volumes (each bound in two parts), published from 1847-1995, contain the transcriptions of ca. 19000 documents dating before 1570 CE.  The texts are transcribed directly and were written in Middle Norwegian, Old Norse, and Latin, among others.  Downloadable scans of these volumes are available through The National Library of Norway (Nasjonalbiblioteket), and links to each bound book listed by volume and part can be found to the right. (As of March 15, 2014, parts marked with * are only available to Norwegian IP addresses, and 3 parts are also not available as e-books.)

There is a searchable interface (Norwegian, English) for these documents made available through the Documentation Project (DocPro) at the University of Oslo, with an associated Norwegian-language mini-help page. 

There are two 'wildcards' that can be used when using the searchable database:
'%' can be used in place of parts of words (in any position)'
'_' can be used in place of single character, and it is possible to use several in a row.
'and' 'or' and 'not' can be used to modify search fields (Norwegian/English) Sammendraget/Regesta (summary), Brevteksten/Text (letter text), Tilleggsopplysninger/Additional information (text on the reverse, seal strings and explanations), and Kilde/Source.

WARINING: The help page clearly states that the searchable version is NOT fully proofread to the printed  version and contains many typos.  The printed version can also contain errors, so for the definitive text, one must seek access to the original manuscripts.  The stated intention of  DocPro is to eventually make images of these available.

USER BE AWARE: It is also important to state a timely reminder that Old Norse and Middle Norwegian were inflected languages.  Middle Norwegian is also a period of major linguistic transition, and the orthographic (spelling) system is not standardized.  Names cannot be automatically lifted from the text and used as printed without considering their grammatical role.  For 'ready to use' names, please consult other sources, such as the name articles found here.

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22. part 1, part 2*
    part 3*