The vector type you use with mtl2lapack functions must be contiguous in memory, and have a function data() defined which returns a pointer to that memory, and a function size() with gives the length.

  double da [] = { 1, 2, 2, 2, 1, 2, 2, 2, 1 };
  lapack_matrix<double,external>::type A(da, M, N);
  lapack_matrix<double>::type B(M*NRHS, NRHS);
  mtl::set(B, 15.0);
  dense1D<int> pivot(N, 0);
  int info = getrf(A, pivot);
  if (info == 0) {
    info = getrs('N', A, pivot, B);

    if (info == 0) {
      cout << "x:" << endl;
      print_all_matrix(B);
    } else
      cout << "Factorization failed with INFO = " << info << endl;
  } else
    cout << "Solve failed with INFO = " << info << endl;

More examples can be found in geequ.cc, gecon.cc, geev.cc