When doing a literature search, it’s a good idea to start from a few articles and then (if they are along the lines of what you are looking for) use their references and articles that reference them to expand the search.
One handy way of doing that is with the HubMed Graph Browser. You get to it by finding an article (like mine here) and then selecting the “Graph” link next to “Related” in the line of options at the bottom.
Once you load the TouchGraph, you can see the related articles, change the depth of relationships graphed, zoom in and out, and so on. It can be a nice alternative to the normal related articles list, graphically showing distance and relation.