The East Germans were using them on the track in the very early 80s (1981 perhaps?), along with the first bladed spokes and suchlike. Bullhorns started being used on the road a few years later. Other countries, including the Americans, chased the technology and Bicycling published some snippets in 1983 in the lead up to the LA Games. The '84 American Team Time Trial team used bullhorns on the road, as did a few others.