Google Scholar is a freely accessible search engine returning only reliable search results that can be cited in research papers (books, scholarly literature, educational sites pages). Using advanced settings, you can choose the years of publication and sort the results by year of publication or relevance.
Another option is to find a friend at a research university and have them download and share the paper with you using the university’s subscription.
There are also less legal options, e.g. sci-hub.tw, that often work when all else fails. Google for more info.