((p "A citation key references some external material that is part of a bibliographical collection.") (p "Currently, Zettelstore implements this only partially, it is " (@L (@H "“") "work in progress" (@H "”")) ".") (p "However, the syntax is: beginning with a left square bracket and followed by an at sign character (" (@L (@H "“") (kbd "@") (@H "”")) ", U+0040), a the citation key is given." " " "The key is typically a sequence of letters and digits." " " "If a comma character (" (@L (@H "“") (kbd ",") (@H "”")) ", U+002C) or a vertical bar character is given, the following is interpreted as " (a (@ (href . "00001007040000")) "inline elements") "." " " "A right square bracket ends the text and the citation key element."))