The first place to look for secondary material is the on-line bibliography associated with this module (but don't forget to select the C18C19.pdt bibliography from the drop down menu!!). Start by typing in just one word from the title - Kabale, Werther, Galotti - as the more you type, the greater the risk of mis-typing something. Don't forget too that you can download the results to your PC - there's no need to copy them pout by hand!).
If an item is listed in the bibliography it is definitely in the library - so ask if you can't find it! You'll find that journal articles will often be of more use to you than books - so get used to consulting those. Almost all the articles cited for this module are available in a digital form ready for downloading in pdf format