Die doppelten Perfektbildungen im Deutschen Eine diachrone Untersuchung

"Overall, the book fills an important research gap as DPFs have not been
empirically investigated diachronically until now. As the main methodological
difficulty has been the rarity of examples of DPFs, the supply of empirical
data is not to be underestimated for its value to further studies. In sum, the
volume thus cannot solve the general puzzles linked with DPFs, but it offers a
wide range of material for addressing them in subsequent investigations."
Sonja Zeman in: Linguist List 24.620