wp-calypso/client/landing/subscriptions/tracks/constants.ts

export const SOURCE_SUBSCRIPTIONS_SITE_LIST = 'subscriptions-site-list';
export const SOURCE_SUBSCRIPTIONS_UNSUBSCRIBED_NOTICE = 'subscriptions-unsubscribed-notice';
export const SOURCE_SUBSCRIPTIONS_SEARCH_RECOMMENDATION_LIST =
	'subscriptions-search-recommendation-list';
export const SOURCE_SUBSCRIPTIONS_ADD_SITES_MODAL = 'subscriptions-add-sites-modal';