Nothing else besides what we see in the NT and other early writings, if that's what you mean. To spell it out a little more, I'm thinking that in Capernaum where he lived, and among the many other disciples besides the twelve, and in the crowds that came to hear him, there would have been people taking notes and writing letters and teaching aids, just like in any other teaching network. Those would have survived long enough to be the Q, L, M and other sources that scholars are imagining. If you have some reasons for thinking that didn't happen, I'm interested.