Pokémon Go Unova Celebration event guide: Field Research and rewards - Polygon

From Jan. 5 until Jan. 10, Pokémon Go is hosting an Unova event that increases the spawn rate of the Pokémon from that region, as well as introducing Shiny Snivy.

Pokémon Go Unova Collection Challenge: How to complete the Collection Challenge and Unova Celebration event field research tasks

Pokémon Go Unova Collection Challenge: How to complete the Collection Challenge and Unova Celebration event field research tasks

Polygon Archives - Pokémon Go guide - Page 12

Pokémon Go Sinnoh Celebration Event guide: Field Research and rewards - Polygon

Massively on the Go: The Pokemon Go outlook for November 2022

Pokémon Go December Field Research tasks and their rewards explained

Polygon Archives - Pokémon Go - Page 7

Unova Celebration Event

Polygon Archives - Pokémon Go - Page 7

Unova Celebration Event - Leek Duck

Pokémon GO Fest 2019 Dortmund, Pokémon GO Wiki