Kochira Katsushika-ku Kameari Kōen-mae Hashutsujo
In 2006, to celebrate the 30th anniversary of "Kochira Katsushika-ku Kameari Kōen-mae Hashutsujo" (or "Kochikame"), a special manga titled was released on September 15. It included characters from the series appearing in special crossover chapters of other well-known manga. The chapter was a "Dragon Ball" crossover by Toriyama and "Kochikame" author Osamu Akimoto. That same year, Toriyama teamed up with Eiichiro Oda to create a single crossover chapter of "Dragon Ball" and "One Piece". Entitled "Cross Epoch", the chapter was published in the Christmas 2006 issue of "Weekly Shōnen Jump" in Japanese and the April 2011 issue of "Shonen Jump" in English. The final chapter of Toriyama's 2013 manga series "Jaco the Galactic Patrolman" revealed that it is set before "Dragon Ball", with several characters making appearances. "Jaco"s collected volume contains a bonus "Dragon Ball" chapter revealing Goku's mother. "Jaco" and the bonus chapter were both published by Viz in their digital English "Weekly Shonen Jump", and later in print.