So I've just finished my undergraduate degree and I'm doing some early preliminary research into potential topics for my Masters dissertation. At current I'm considering looking at perhaps the Reconquista of Iberia, Hanseatic trade in the Baltic, or perhaps the Teutonic and Livonian Orders. I'm wondering if anyone could suggest any primary source material for these areas, or if anybody has any knowledge of source books pertaining to these topics. I've had a brief look at Fordham's medieval source book, but a number of links are unfortunately broken, or are limited on some of these topics. I apologise if anyone has asked a similar question before, but thanks in advance.
A really big part of earning an advanced degree in history is learning to do this on your own: identifying a topic, learning the literature, and locating appropriate sources are pretty much the bread and butter of doing historical research.
In addition to what /u/agentdcf has written, what languages do you know? In general, historical research is done in the original languages where possible. Are you asking for Latin sources? Or could you manage Medieval German or Spanish sources?
As for what /u/agentdcf is saying, a day or two pulling books off shelves in the library should be enough to do it. It's often what I did at the start of a research project--I just pulled out every possibly relevant book at a big university research library and set myself down at a table to breeze through all of them (come after a meal because food is often the limiting factor--also, I wrote a lot of little signs that said "Please do not reshelve these books on x/x/20xx, I've just stepped out to eat and should return shortly").
Since our rules DO permit people to ask for help with their homework -- or in this case advanced degree --, so long as they are seeking clarification or resources, rather than the answer itself, I will permit this question.
However, as /u/agentdcf has pointed out below, it is an integral part of earning an advanced degree in history to identify a topic, learn the literature and find the best sources. The whole point of having people write these texts is for them to learn it and to demonstrate proficiency in what is the very essence of our discipline: The production of texts based on research and theory.
I would first and foremost recommend you talk to your professor(s) for further help and while we do have our six-part series, "Finding and Understanding Sources", I can not stress the importance of doing exactly this part of the process yourself enough.