From the Google Scholar Blog:
Today, we are releasing Classic Papers, a collection of highly-cited papers in their area of research that have stood the test of time. For each area, we list the ten most-cited articles that were published ten years earlier.
This release of classic papers consists of articles that were published in 2006 and is based on our index as it was in May 2017.
To browse classic papers, select one of the broad areas and then select the specific research field of your interest.
The list of classic papers includes articles that presented new research. It specifically excludes review articles, introductory articles, editorials, guidelines, commentaries, etc. It also excludes articles with fewer than 20 citations and, for now, is limited to articles written in English.
Direct to Classic Papers List of Categories
Direct to Library Science Category
At the bottom of each list of Classic Papers you’ll find the following statement:
Dates and citation counts are estimated and are determined automatically by a computer program.
Direct to Complete Blog Post
Note: As of June 7, 2017 we were unable to locate any additional documentation about Classic Papers. If/when more info becomes available we will update this post.