Routine plea: please link to abstracts (Šuvakov and Dmitrašinović - Three classes of Newtonian three-body planar periodic orbits - https://arxiv.org/abs/1303.0181) rather than directly to PDFs. (It is an easy click to get from abstract to PDF, but not vice versa.)

That's good advice. Thanks! I've switched a couple of the links to abstracts instead of PDFs, though what I really need is a proper references section since direct links are also convenient—if they work.