We got invitation letter from chinese company

a friend of mine advice me to get invitation letter of Duly Authorized Unit; but I have Australian passport and my business partner have Somalia passport both of us have official invitation letter from Chinese company. Do we need to get Invitation letter of Duly Authorized Unit to get Chinese visa from Djibouti or we can proceed our travel to Djibouti. Please can you advice us. thanks

from Ayanle