uBlass outer_product

Hi, I can't get the following snipped from the doc examples to work: #include <iostream> #include <boost/numeric/ublas/vector.hpp> #include <boost/numeric/ublas/io.hpp> int main () { using namespace boost::numeric::ublas; vector<double> v1 (3), v2 (3); for (int i = 0; i < std::min (v1.size (), v2.size ()); ++ i) v1 (i) = v2 (i) = i; std::cout << outer_prod (v1, v2) << std::endl; } ublas_cross.cc: In function `int main()': ublas_cross.cc:17: `outer_prod' undeclared (first use this function) ublas_cross.cc:17: (Each undeclared identifier is reported only once for each function it appears in.) What's wrong here? Thanks Olaf