Cheers, marcus. You're way too kind.
Luckily, the OP seems to have left, so I won't have to try and possibly fail at living up to the hype. Perhaps your mentioning of Hohmann transfer orbits was enough after all.
But in case he does come back sometime later, and so as not to make your post - praising a single sentence - look like a sarcastic quip, let me add some hopefully useful ramblings.The thing about orbital manoeuvres is that they've been mostly figured out theoretically by the early pioneers like Hohmann, Oberth and Tsiolkovsky some hundred years ago. As such, they will be covered not in original scientific papers, but in venerable textbooks.
The Hohmann transfer orbit is one such age-old concept. Any college-level introductory book on astronomy will have it at least mentioned. A dedicated book on orbital mechanics will do so in more detail.
If you can't access, or be bothered to sift through such books, there is also a plethora of very good material available online.
The very basics presented conceptually only can be found on the NASA website:
http://www2.jpl.nasa.gov/basics/bsf4-1.php
and a fine rigorous treatment is accessible from MIT open courseware:
http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-07-dynamics-fall-2009/lecture-notes/
(lecture #17 specifically - it's in-depth but doesn't require any advanced calculus)
In general, the fundamentals of Hohmann transfer orbits can be understood with little more than energy conservation equations.
As far as I can tell, most of advancements in the area are left to the engineering and number crunching side of things. But there is some theoretical research trying to fine-tune some of the details too. This paper, for example:
Earth--Mars Transfers with Ballistic Capture; F.Toputto, E.Belbruno
is one of such attempts. If this is the level of 'in-depth studies' required, then I'd advise to follow the sources from that article and see where they get you.
