If so, include this information in the syllabus. It's cumbersome to constantly grade these things. Students are often insulted by the practice. Most importantly, students often end up directing their focus, not on reading critically, but on trying to figure out what the quiz will cover. Early in the course acknowledge that some of the reading will be quite challenging and that you will help them develop strategies for reading the material effectively.
Students are often embarrassed to admit that they have difficulty completing the assigned reacting.
They are surprised to encounter texts that are difficult for them to understand. When inviting students to come by our offices to discuss rough drafts and burning question, remember to invite students to seek us out if they have trouble with the reading assignments. Such an invitation helps reassure them that you expect the reading will be challenging and that they should not be ashamed if they experience difficulty. Before students begin to read a new assignment, consider what information they may need before they begin. I have found it worthwhile to spend a few minutes at the end of class session to prepare students for their next assigned reading.