Please do not put Category:Traken into category:Planets visited by the Fourth Doctor. Instead, put the page Traken into the category. This reduces unnecessary category tree recursion — surely a goal of which Nyssa of Traken would approve.
“The Traken Union (or Empire of Traken) was a group of five or six allied planets centred around...Traken Union
“Serenity was a colony of the Traken Union located at the edge of the Mutter's Spiral. It was...Serenity (Cold Fusion)
“The Keeper of Traken, or simply the Keeper, was the leader of the planet Traken and of the...Keeper of Traken
“The Benign Union, which the Sixth Doctor considered not to be benign, was the new empire of...Benign Union