On regular algebraic surfaces of $R^3$ with constant mean curvature
  We consider regular surfaces $M$ that are given as the zeros of a polynomial function $p:R^3\rightarrow R$, where the gradient of $p$ vanishes nowhere. We assume that $M$ has non-zero mean curvature and prove that there exist only two examples of such surfaces, namely the sphere and the circular cylinder. 
Jo\~ao Lucas Marques Barbosa and Manfredo Perdig\~ao do Carmo
math.DG