545 Subfield $b - Expansion:

Subfield $b contains an expansion of the biographical or historical data given in subfield $a .

Example:

545 1#$aThe Office of Geography provides research and other staff services for the interdepartmental Board on Geographic Names and the Secretary of the Interior on foreign geographic nomenclature.$bThe Office inherited functions and records of earlier boards and committees engaged in similar work. The earliest of these, the U.S. Board on Geographic Names, was created by an Executive order of September 4, 1890, to ensure uniform usage throughout the executive departments of the Government ...