フィードをオートディスカバリーする XPath

こんな感じ

document.evaluate('/html/head/link[contains(concat(" ", @rel, " "), " alternate ") and (@type = "application/x.atom+xml" or @type = "application/atom+xml" or @type = "application/xml" or @type = "text/xml" or @type = "application/rss+xml" or @type = "application/rdf+xml")]', document, null, 7, null)

ブックマークレットにしてみる

javascript:var ___r=document.evaluate('/html/head/link[contains(concat(" ", @rel, " "), " alternate ") and (@type = "application/x.atom+xml" or @type = "application/atom+xml" or @type = "application/xml" or @type = "text/xml" or @type = "application/rss+xml" or @type = "application/rdf+xml")]',document,null,7,null);for(var ___t=[],___i=0;___i<___r.snapshotLength;___i++)___t.push(___r.snapshotItem(___i).href);alert(___t.join('\n'));

でも、この辺あまり詳しくないんです＞＜
あまり、自身ないっす