I have been trying to find the papers of Nagell and Ljunngren, which deal with the equation $$\frac{x^n - 1}{x - 1} = y^2$$ and solve it completely. Many papers cite these papers, but I haven't found them anywhere. If anyone can provide some information, I would be very grateful.
Here are some links of the papers which cite it: http://www-irma.u-strasbg.fr/~bugeaud/travaux/PredaYann1.ps
http://projecteuclid.org/download/pdf_1/euclid.pjm/1102620327