If you are looking for specific types of papers or research, you might find better results by refining the query:
Open directories are uncurated. Files found here are not scanned for malware by a hosting provider. Downloading an "updated" from an open directory is a high-risk activity. Ethics & Legality (Variable): intitle index of updated
By using the Google "dork" (a sophisticated search string) intitle:"index of" , you are telling the search engine to only return pages where that specific phrase appears in the HTML title tag. Why Add "Updated"? If you are looking for specific types of