Here is how I decided to "cite" the barn that has the year of immigration for one of my families that was mentioned in an earlier post:
Edward Habben Farm (Hancock County, Illinois, west of Carthage on Highway 136, southeast corner of the southeast quarter of section 21 in Prairie Township), barn, personal observation by Michael John Neill, September 2012.
I decided to pattern off the rural grave marker model in Elizabeth Shown Mills' Evidence Explained. .