This online course was released in 2024. This course goes into much more detail not only on how to learn markers but also how to apply them in behavior creation. In 2008 Ed Frawley, the owner of Leerburg, released his first  DVD on the subject of Marker training. That material and more was turned into an online course in 2015. That course is being redone and updated with additional training material and is being released in late 2023 or early 2024. | Links mentioned: The Power of Training Dogs with Markers -  https://university.leerburg.com/Catalog/viewCourse/cid/96