1982, Peter Gollwitzer wrote a whole book about this, and in 2009, he did some new tests that were published.
1982: Петр Гоулвитцр энэ тухай ном бичсэн бол 2009 онд хэдэн шинэ туршилт хийж, үр дүнг нь нийтэлсэн байна.