On the potentials yielding cosmological scaling solutions
  In the present work we perform a phase-plane analysis of the complete dynamical system corresponding to a flat FRW cosmological models with a perfect fluid and a self-interacting scalar field and show that every positive and monotonous potential which is asymptotically exponential yields a scaling solution as a global attractor. 
Ana Nunes (U. Lisbon) and Jose P. Mimoso (U. Lisbon)