If what you know has been published in a way which meets enwp.org/WP:Reliable_sources then it can be used in articles. Unpublished material can't be used, becau

If what you know has been published in a way which meets enwp.org/WP:Reliable_sources then it can be used in articles. Unpublished material can't be used, because it can't be independently verified by anyone - see enwp.org/WP:V Self-published material might be usable under certain circumstances, if you're already an established expert in your field (per independent reviews, or citations by others) - see enwp.org/WP:SPS