Use Wikipedia to verify basic facts.
Paper of Record: A national paper of record is a reputable paper that attempts to cover all important national news with staff reporters. They are distinguished from regional and local papers which use staff primarily for local or regional news.
Grassroots organizations are organizations which are primarily run and funded by interested citizens and independent activists.
Professional organizations provide an array of services and support to people in a given field or profession.
What's lateral reading?
Lateral reading is using other websites and sources to verify claims and content on websites you are evaluating. It is a strategy used by professional fact-checkers. It's as simple as opening up a few more windows on your browser and searching other sites for claims, persons, things, and events to verify content as your read the source page.
It's different than vertical reading, which is when you stay on a website and follow the links or analyze the content on your source page without verifying with outside sources.