Anannia, non different teachers. Literally, nanania means not different. Here he says, a prita ducina acariena, the master who is, who does cuses oneness. The one who teaches in that way, teaches mens, of course, doesn't just you are brahman,. It's done. There is no further cogitation with regard to it.
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of the most popular Upanishads. The scripture concerns the story of a young man who goes to the house of death to find out what happens after death. The reply describes the nature of reality and the meaning of life.