  Inclusive doubly differential cross sections d^2\sigma_{pA}/dx_Fdp_T^2 as a
function of Feynman-x (x_F) and transverse momentum (p_T) for the production of
K^0_s, Lambda^0 and anti-Lambda^0 in proton-nucleus interactions at 920 GeV are
presented. The measurements were performed by HERA-B in the negative x_F range
(-0.12<x_F<0.0) and for transverse momenta up to p_T= 1.6 GeV/c. Results for
three target materials: carbon, titanium and tungsten are given. The ratios of
production cross sections are presented and discussed. The Cronin effect is
clearly observed for all three V^0 species. The atomic number dependence is
parameterized as \sigma_{pA} = \sigma_{pN} \cdot A^\alpha where \sigma_{pN} is
the proton-nucleon cross section. The measured values of \alpha are all near
one. The results are compared with EPOS 1.67 and PYTHIA 6.3. EPOS reproduces
the data to within \approx 20% except at very low transverse momentum.
