Pick two of the papers from the readings of one lecture topic and write a 2-3 page summary of the two works, discussing similarities and differences in the approaches and/or findings in the context of the specific tasks that they tackle. The differences could be due to genre, assumptions about annotated data, linguistic analysis, advances associated with a time difference of the articles, etc. At least one of the two papers should be from the list of optional readings.
The following provides examples (but not a requirement) of discussions you might include:
The style of your discussions should be similar to a paper review: highlight useful results, but do not be afraid to point out limitations of the methods. If you are ambitious or know something about work in the area of either paper you have chosen, then you can expand on any of these points and discuss findings in related work that confirm the results or point out limitations.