Code changes to reflect data curation and cleanup results

cd8b9d8d559c8bc256264cbcd56a6713dc5dd801
* Changes directory of datafile.
* Use correct column for date that is used as data publication date.
* Accounts for NA entries in Google Scholar search query hits.

d2745fd9d6e2a6eba85218ae89db619bb3f64494
* Changes selection of reference, because we now know exactly in which column to expect it.