DOI Data Dictionary, 2015-03-23

iso3166a2:BA	MT	Bosnia and Herzegovina.
Baseline	MT	A Baseline Identifier, a 7-digit identifier for audiovisual works.
iso3166a2:BB	MT	Barbados.
iso3166a2:BD	MT	Bangladesh.
iso3166a2:BE	MT	Belgium.
Before	MT	The Relator between a time and another before which the first occurs.
iso3166a2:BF	MT	Burkina.
iso3166a2:BG	MT	Bulgaria.
iso3166a2:BH	MT	Bahrain.
iso3166a2:BI	MT	Burundi.
iso3166a2:BJ	MT	Benin.
iso3166a2:BL	MT	Saint Barthélemy.
Blog	MT	A blog (weblog) on a website.
BlogEntry	MT	An entry in a Blog.
iso3166a2:BM	MT	Bermuda.
iso3166a2:BN	MT	Brunei.
iso3166a2:BO	MT	Bolivia.
Book	MT	A non serial Creation, capable of being expressed in printed form with multiple bound pages and covers, published with a distinct Title and not as part of another Publication unless it is set of similar Resources. A DOI applied at this level may refer to a Book which appears in physical, digital and audio forms.
BookChapter	MT	A Chapter of a Book.
BookPublisher	MT	A Publisher of Books.
BookSeries	MT	A Series of Books.
iso3166a2:BR	MT	Brazil.
iso3166a2:BS	MT	The Bahamas.
iso3166a2:BT	MT	Bhutan.
iso3166a2:BV	MT	Bouvet Island.
iso3166a2:BW	MT	Botswana.
iso3166a2:BY	MT	Belarus.
iso3166a2:BZ	MT	Belize.