DD-WRT firmware flash on Tp-link Archer C9 Router (Ver. 1) - Step by Step - guide - YouTube
Amazon.com: TP-Link AC1900 Smart Wireless Router - Beamforming Dual Band Gigabit WiFi Internet Routers for Home, High Speed, Long Range, Ideal for Gaming (Archer C9) : Electronics
User manual TP-Link Archer C9 (English - 143 pages)
C9 AC1900 Wireless Dual Band Gigabit Router User Manual TP-Link Technologies