These data are yields in bushels per acre, of 10 varieties of barley
  grown in 1/40 acre plots at University Farm, St. Paul, and at the five
  branch experiment stations located at Waseca, Morris, Crookston, Grand
  Rapids, and Duluth (all in Minnesota).  The varieties were grown in
  three randomized blocks at each of the six  stations during 1931 and
  1932, different land being used each year of the test.
Immer et al. (1934) present the data for each Year*Site*Variety*Block.
  The data here is the average yield across the three blocks.
Immer et al. (1934) refer (once) to the experiment as being conducted
  in 1930 and 1931, then later refer to it (repeatedly) as being
  conducted in 1931 and 1932.  Later authors have continued the
  confusion.
Cleveland (1993) suggests that the data for the Morris site may have
  had the years switched.