  Let Y be a normal crossing divisor in the smooth projective algebraic variety
X (defined over ${\mathbb C}$) and let U be a tubular neighbourhood of Y in X.
We construct homological cycles generating $H_*(A,B)$, where (A,B) is one of
the following pairs $(Y,\emptyset)$, (X,Y), (X,X-Y), $(X-Y,\emptyset)$ and
$(\partial U,\emptyset)$. The construction is compatible with the weights in
$H_*(A,B,{\mathbb Q})$ of Deligne's mixed Hodge structure.
