I'm trying to read more into the Lagrange-Gibbs F and G solutions for orbit determinations, but I just can't seem to find anything on it. It's in the lecture slides and in the textbook, but when I do a simple google search, I am not getting anything. The theory is correct and all, so I'm pretty sure it's an official technique, but I can't seem to find any more information on it. What's the reason behind this? Is it because it's not widely used / and is obscure? And what can I do if I'm trying to read more into a topic and I'm not finding anything through a simple google search?