===== BNF of BNF =====

<ebnf> "Backus-Naur Form" {
  syntax         = rule [ syntax ] .
  rule           = opt-ws  identifier opt-ws "::=" opt-ws expression opt-ws EOL .
  expression     = list [ "|" expression ] .
  line-end       = opt-ws EOL | line-end line-end .
  list           = term [ WHITESPACE list ] .
  term           = literal | identifier .
  identifier     = "<" character {character} ">" .
  literal        = "'" {character} "'" | '"'  {character} '"' .
  opt-ws         = { WHITESPACE } .
  character      = lowercase-char | uppercase-char | digit | special-char .
  lowercase-char = "a" | "b" | "..." | "z" .
  uppercase-char = "A" | "B" | "..." | "Z" .
  digit          = "0" | "1" | "..." | "2" .
  special-char   = "-" | "_" .
} </ebnf>