After writing about Groundhog Day, I did hunt around to read a bit about the film.
Interestingly, it seems that the final product was really a collaborative effort between the screenwriter, Danny Rubin (who had written a very different script), Ramis, and Murray. Ramis, of course, directed its development from the original script, but Murray was difficult and insistent about the character, and the result was the film as it is. Murray was so difficult, that he and Ramis - despite their long relationship prior - did not speak again until the end of Ramis' life.
I am posting a few links.
First, as expected, Wikipedia has a long entry which is helpful, and has 76 references.
Here's an interview with the screenwriter, Danny Rubin.
Of course, Mark Steyn knows and enjoys the Brigadoon reference.
A 2003 NYT article about a MOMA conference on God and Film opening with Groundhog Day.
Jonah Goldberg at the National Review on the film.
An oft-cited piece which is really quite good and worth reading on the themes, but takes a few missteps - the local man named "Gus" is clearly short for Augustine? Unlikely. The analogy regarding the "shadow" cast by the two Phils is excellent, however, and obvious in retrospect.
Another Christian piece that reflects on the nature of and possibility of human virtue in a fallen world.
A four minute video of Ramis about the film.
Last, a long 80 minute video where Ramis is presenting at a conference on cinema. At 1:09:30 he speaks about his personal quest for meaning - and for laughs. It's worth watching if you think that Groundhog Day is explicitly certain about a cosmic teleology - as opposed to nature being consistent with the possibility of one.