Perhaps you should try some spelling variations:
history mexican » history american, history mexico, history lexicon
history medical » history medieval, history media, history medicine
lectures de » lectures _, lectures 1, lectures 2
lecture de » lecture _, lecture 1, lecture 2

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((lecture de) OR (lectures de)) ((history mexican) OR (history medical)).
• Adding a wildcard symbol may retrieve word variants: ((lecture de) or (lectures de)) ((history mexican) or (history medical))*.