Copious further discussion of primary, secondary, and tertiary sources can be found on the Internet. Helpful websites and Web-based videos are listed here.
Use Google Scholar to find academic-quality information (articles, papers, reports) on the Web.
Find more discussion of source types, along with many examples, here:
The University of Maryland Libraries
The University of St. Thomas Libraries / Research Tools (Source Types)
The University of St. Thomas Libraries / Research Tools (Source Type EXAMPLES)
The University of Wisconsin Library / University Library
Prmary, Secondary & Tertiary Sources -- A Brief Explanation / The Beam Library (YouTube)
Primary, Secondary, Tertiary -- The David L. Rice Library (YouTube)
Primary vs Secondary Sources -- Alexandra Razgha (YouTube)
What is a Primary Source? -- Geisel Productions (YouTube)