@chris-richards I used the Subcorpora that is available for the open access version. Just go to Word Sketch – Advanced and select AH, SS, PS or LS.
But, in order to see the topics, I went to the concordance of a specific collocation (develop + theory) and clicked on the i button (the View line detail options button) (step 1). Then, I unticked the Text genre (step 2) and ticked the Document title (step 3) before saving (step 4). Once you are back to your concordance, you can hover your mouse over the i button and you will see the full title of the document popping up.