1.		Digital local, transit, combined and international exchanges in integrated digital networks and mixed analogue-digital networks : supplements: recommendations Q.500-Q.554 / International Telecommunication Union Data Publicação: 1989 Tema: Vária
2.		Digital networks, digital sections and digital line systems : recommendations G.801 - G.961 / International Telecommunication Union Data Publicação: 1989 Tema: Vária