\] Assume that $a \in { L^\infty ( {{{\bf}R}}_+ ; W^{0,\infty}({{{\bf}R}}^d ))}{}$, $(0 + |v|^0) { f ^{\mathrm{in}}}\in { {\cal M}_b ^+ ({{{\bf}R}}^d \times {{{\bf}R}}^d)}{}$, ${ \mathrm{supp\;}}{ f ^{\mathrm{in}}}\subset \{(x,v) :|