Just returned from the Giekau Family History Fair in Emerson, NE. My ancestors spelled the last name in many ways--Dose, Doose, Dohse, Dosen (females), etc. Check out the web site for the fair at http://www.giekau.com
There will be another one in June or July 2008 in northwest Iowa. Two years ago it was held in Mineola, IA. Many people in both areas had ancestors from the Giekau area.