In the late 1960s, similar ideas reappeared, beginning with John Ostrom's work on "Deinonychus" and bird evolution. His student, Bob Bakker, popularized the changing thought in a series of papers beginning with "The superiority of dinosaurs" in 1968. In these publications, he argued strenuously that dinosaurs were warm-blooded and active animals, capable of sustained periods of high activity. In most of his writings Bakker framed his arguments as new evidence leading to a revival of ideas popular in the late 19th century, frequently referring to an ongoing "dinosaur renaissance". He used a variety of anatomical and statistical arguments to defend his case, the methodology of which was fiercely debated among scientists.