@article {jue:93d, author = {B. J{\"u}ttler}, title = {{\"U}ber zwangl\"a{}ufige rationale {B}ewegungsvorg\"a{}nge}, journal = {Sitzungsber. \"O{}sterr. Akad. Wiss., Abt. II}, volume = {202}, year = {1993}, pages = {117--132} }