To the bibliography for Italian given on pg. 503 add Michel 1997. This is a very interesting account of the historical grammar of Old Italian with a good selection of commented texts in a variety of dialects. From this book I learn that the historical interpretation of the Italian masc. sg. article il that I give in the book (p. 522) , i.e. < *illī is probably not correct. Instead il is prothetic from form earlier (')l as in dove 'l sol tace (Dante Inf. 1.60) < *ubi illum sole tacet. Another form found in Tuscan until the 16th century is el, which perhaps is from illum with apocope, although this too is not certain.
Michel, Andreas, 1997. Einführung in das Altitaliensche. Tübingen: Gunter Narr.