Two sources aren't enough, at least for the general case. You'll need at least 3 to locate a point in 2D space, and 4 to locate a point in 3D space. More can be better, if your device can handle the math.
This is a seriously non-trivial problem. We had some students working on an AGV project that used 5 specialized radios that cost several hundred dollars each for a similar project (the space was ~30m square, not sure how far it would have scaled up).
-j