Refrences

• [KM] M. Kapovich, J. Millson, Universality theorems for configuration spaces of planar linkages, Annals of Math., submitted.
  
  
• [N] J. Nash, Real algebraic manifolds, Annals of Math. 56 (1952) 405-421
  
  
• [T] A. Tognoli, Su una congettur di Nash, Ann. Sc. Norm Sup. Pisa 27 (1973) 167-185