Ringe- displaced imperatives

From: jackangstreich
Message: 71316
Date: 2013-09-18

In Donald Ringe's discussion of reconstruction of PIE verbal morphology in his book on the history of PIE to Proto-Germanic he cites a few forms as displaced imperatives in the table on page 31 -- can anyone explain what these are? what is a "displaced imperative" in this context? -- he doesn't seem to explain these forms in the book