Select node by node name or type alias

I have a group of news articles that need to be pulled in for a for a slideshow.
I am trying to grab only the articles saved in a node type of “NewsCategory”, but only within the node with the alias of “Alumni”. Here is what I have, but it’s not pulling anything in. What’s wrong with my syntax?

<xsl:variable name="articleNode" select="$siteRoot/NewsHome/NewsCategory[@alias='Alumni']/DateFolder" />

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/74072-select-node-by-node-name-or-type-alias