David Mason, Pangborn's paradox (1958)
“ Doctor Randall said, from far down in his comfortable chair. "No such thing as time travel.""You underestimate the Physics department," Pangborn told us coldly. "In spite of heavy losses to our staff—last year's treason trials cost us three of our most brilliant young men—we've made some very remarkable strides. We have what is crudely termed a time machine—although the correct term is temporal transducer. In fact we are currently conducting some very interesting researches with it.""Then you have tried the killing of a grandfather, Herr Doctor?" Von Juntz inquired. ”
