uri rfc (rfc|bcp|std)\d+ rfc-errata draft (draft|RFC)(-[a-zA-Z0-9]+)+ registry person text note unicode ucd\d+\.\d+\.\d+ (\d+|0x[\da-fA-F]+)(\s*-\s*(\d+|0x[\da-fA-F]+))? 0x[0-9]{8} [0-1]+ legacy mib template json