Yesterday I was looking for and found many of my relatives in the 1920 Census for NE, Butler Co., David City - Enumeration Districts #s 4,5,6, & 7. In my search of these districts, I saw several Prochaska families if I remember correctly. I have 4 more districts to go thru and there are probably more Prochaskas to be seen. Hope this helps. Census records may be time consuming to search if there is no index, but is certainly worth the time and expense.