During his time on Vanaheim, Oswald also took a large number of notes, wrote scrolls, drew reference pictures, and wrote other books. These are discovered by the Dragon Riders on successive visits to Vanaheim.
In "Searching for Oswald... and Chicken", the Riders leave Vanaheim, with Fishlegs flying away with a large stack of tomes written by Oswald. This stack includes hundreds of recipes for fruit.
Oswald also wrote extensively about dragons and dragon species. Fishlegs discovered the Ingerman family originally came from the Dragon Hunters through Oswald's notes in the episode, "Loyal Order of Ingerman".
Even though Fishlegs left with many of Oswald's papers, there are still more writing left at his hut on Vanaheim. In "Guardians of Vanaheim", when the Riders return to Vanaheim to stop a group of Dragon Flyer scouts from telling Johann the secret of Vanaheim, they discover all the Sentinel dragons have been apparently killed. Fishlegs stays behind, as Meatlug does not want to leave the deceased dragons. Fishlegs eventually realizes due to Meatlug's actions that they are not dead, but rather in a form of recuperative coma. He rifles through the remaining items in Oswald's hut and finds details about Sentinel healing.
Fishlegs once again refers to Oswald's papers when comparing a Titan Wing Dramillion with a drawing of the 'King of Dragons' skeleton on Vanaheim. He determines they are not the same species.
Fishlegs, ever studying, mentions Oswald's notes in the game School of Dragons during the "Wrath of Stormheart" Expansion. He recalls reading about the Elder Sentinel in the notes.