===Identify Clean Data (Round 2)===
A new list of city names cities is extracted in Section 4.3.2. This list, combined with 'ptoassigneend_us_citylist', generates a new city list 'ptoassigneend_us_citylist2' which can be used to identify clean data.
Since the city list is not long, I briefly cleaned the list by hand, and stored it in ptoassigneend_us_citylist2.