Hanna-Barbera 

William Hanna (Left) and Joseph Barbera.

Three examples of animations by Hanna-Barbera

Scooby Doo Where are you? intro.

The Smurfs inro.

Swat Kats intro.

Five websites with information on Hanna-Barbera

https://www.kidswb.com/

https://en.wikipedia.org/wiki/Hanna-Barbera

https://www.angelfire.com/stars/ScooobyDooobyDooo/hbinfo.html

https://www.kidzworld.com/article/2230-hanna-barbera-biography