Codex – Snippets – WooCommerce – https://woocommerce.com/documentation/woocommerce-codex/snippets/
WooCommerce Conditional Logic – Tags, Examples & PHP – https://www.businessbloomer.com/woocommerce-conditional-logic-ultimate-php-guide/
How to change the city field to a dropdown – https://jeroensormani.com/changing-the-city-field-to-a-dropdown/