I should also mention that there is another and totally unrelated way in RM to find where sources are used that does not involve a report at all. Namely, you can search for them. There are two ways to conduct such a search.
The first way is to click on the looking glass icon on the tool bar and then click on Find. You will be in RM's Search for Information dialog. For searching people, you can search on something like Sources (general)->Name contains->"name of your source". You can also search on many other aspects of your source such as Footnote contains. For searching events, you can search on something like Any fact->Source->Name contains->"name of your source", etc. You can also combine these two searches together into a single search with a Boolean AND or OR operator. The OR operator would probably be most valuable in this case. The search will take you to each person meeting the criteria, one person at a time. Having reached that person, you will still have to hunt around to find where the matching source is found.
The second way is FInd Everywhere which may be found by Search->Find Everywhere... from the menu bar. In general, the Find Everwhere report is a much nicer report than is the Lists->Source list... report. For one thing, it is a so-called live report. So you don't have to print the report to a file. You can click on items directly in the report to see them and edit them. But it doesn't really find everywhere. Rather, it finds in lots of places but not really everywhere. That doesn't matter for your purposes because it does find in sources. But when it finds in sources, it doesn't really give you enough information to tell you where all the sources are. Other parts of Find Everywhere are very strong and useful in the way they work, but the sources part of Find Everywhere is actually not quite as useful as you might wish.
Well,there is sort of a third way, but it's really a variation on the theme of the first way. You can do the same kind of searching to make a group. Having done so, you can place the group in the sidebar on the left side of the RM screen or you can go into People View and select the group you have just made. Either way, you can see all the people who contain the source in question. But if you edit such a person, you will still have to search around in the person to find where the source is used.