The creators of Yakuza / Like a Dragon: Infinite Wealth, Ryu Ga Gotoku Studio, have given some explanation for the series title change
Yakuza 3, Yakuza Wiki
RGG Studio Director and Yakuza Series Producer Talk About Like a Dragon Gaiden, the New Agent Style, and Tom Cruise - One More Game
Yakuza: Like a Dragon exam answers: How to pass every exam at the Ounabara Vocational School
Like a Dragon Ishin review — 'just great' is enough for Yakuza rebirth
Yakuza's Kazuma Kiryu is back in Like a Dragon 8 and a new spinoff - Polygon
New Like a Dragon Gaiden trailer reveals spy gadgets, mini-games
The American Misunderstanding of Masculinity in the “Yakuza” Series, by Ethan Huang, The Ends of Globalization
Yakuza 8 is now also Animal Crossing, apparently - Boing Boing
Kazuma Kiryu - Wikipedia
The Complete List of Yakuza Games in Chronological Order - Cheat Code Central
Why did Sega change Yakuza to Like a Dragon? We asked the devs and learned that the title Like a Dragon 8 isn't finalized yet - AUTOMATON WEST