What are these?

Social bookmarking is an activity performed over a computer network that allows users to save and categorize personal collection of bookmarks and share them with others. Users may also take bookmarks saved by others and add them to their own collection, as well as subscribe to the lists of others - a personal knowledge management tool.

For further information, take a look of the Wikipedia description.

Pakistan Journal of Zoology

Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'research_links.snf_archives.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by