Spin http://www.oal.ul.pt/~acorreia/cvpubs/venus1.pdf Long term evolution of the spin of Venus I. Theory Alexandre C.M. Correia, Jacques Laskar, and Olivier NerĂ²n de Surgy http://www.oal.ul.pt/~acorreia/cvpubs/venus2.pdf Long term evolution of the spin of Venus II. Numerical Simulations