PCC Task Group on AACR2 & RDA Acceptable Heading Categories AACR2 headings valid under RDA with no change 7,631,000 records (about 95.1% of AACR2 records) AACR2 headings in need of mechanical changes to be valid under RDA 172,000 records (about 2.1% of AACR2 records) AACR2 headings containing elements not provided for by RDA or that are lacking required elements.
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