This thesis by Christian Caspers from the University of Duisburg/Essen gives you over 200(!) references on the subject in addition to the thesis itself. I think you will find the answers you are looking for, if not, I would contact Christian directly.
You are welcome! If Christian's thesis is good, you should recommend it to others (I do not know him, but I am sure he will appreciate it!). Also, if you happen to be interested in the (structural) behaviour of the trivalent europium ion, as well as all the other lanthanoid(III) ions, you could always read my coordination paper on the subject:
"Structural study of the N,N'-dimethylpropyleneurea solvated lanthanoid(III) ions in solution and solid state with an analysis of the ionic radii of lanthanoid(III) ions", Inorg. Chem. 2010, 49, 4420-4432.