Ideographs such as Unihan ideographs are also categorized as "other letters". As of Unicode 13.0, Unicode defines a total of 92,856 CJK Unified Ideographs. The Supplementary Planes contain emoji, historic scripts, less used symbols, less used Chinese ideographs, etc. Also in CJK Unified Ideographs Extension B, hundreds of glyph variants were encoded. GB18030-2000(includes GBK and all Big-5 characters mapped to Unicode CJK Unified Ideographs and Extension A). In CJK Unified Ideographs Extension B, some characters are incorrectly unified with others. Seventy-three CJK Ideographs that represent a number, including those used for accounting, are typed Numeric. In addition to Unicode (with the set of CJK Unified Ideographs), local encoding systems exist. It is one of the source standards for Unicode's CJK Unified Ideographs. Peter Boodberg and William Boltz have argued that no ancient characters were compound ideographs. The mathematical ideas exhibited by those ideographs are transformational geometry, abstract algebra and linear algebra. Standard Chinese ideographs are often used in this situation to avoid ambiguity. This is a Supplementary Plane used for Chinese, Japanese, and Korean ideographs. Patterns often have their origins in early ideographs. The second volume, covering Han ideographs, was published in June 1992.