Linking within SGML documents can be confusing, so here is a summary: Intra-document Linking ---------------------- use to get chapter/section number from the title of the target link, or xreflabel if defined at the target, or refentrytitle if target is a refentry; has no close tag http://www.oasis-open.org/docbook/documentation/reference/html/xref.html use to supply text for the link, requires http://www.oasis-open.org/docbook/documentation/reference/html/link.html linkend= controls the target of the link/xref, required endterm= for , allows the text of the link/xref to be taken from a different link target title External Linking ---------------- like , but uses a URL (not a document target); requires ; if no text is specified, the URL appears as the link text http://www.oasis-open.org/docbook/documentation/reference/html/ulink.html url= used by to specify the URL, required Guidelines ---------- o If you want to supply text, use , else o Do not use text with so the URL appears in printed output o Specific nouns like GUC variables, SQL commands, and contrib modules usually have xreflabels