Differential Calculus on Quantum Spheres
  We study covariant differential calculus on the quantum spheres S_q^2N-1.   Two classification results for covariant first order differential calculi are proved. As an important step towards a description of the noncommutative geometry of the quantum spheres, a framework of covariant differential calculus is established, including a particular first order calculus obtained by factorization, higher order calculi and a symmetry concept. 
Martin Welk