Other western music yodeling singers include Douglas B. Green (Ranger Doug) and Wylie Gustafson. Green sings with his band Riders in the Sky. He is also a music historian and has written a book, "Singing in the Saddle," described as "the first comprehensive look at the singing cowboy phenomenon that swept the United States in the 1930s." Gustafson learned to yodel from his dad, who learned from Austrians on the ski team in Bozeman, Montana. In 2007, he released an instructional book and CD.