  For any two disjoint oriented circles embedded into the 3-dimensional real
projective space, we construct a 3-dimensional configuration space and its map
to the projective space such that the linking number of the circles is the half
of the degree of the map. Similar interpretations are given for the linking
number of cycles in a projective space of arbitrary odd dimension and the
self-linking number of a zero homologous knot in the 3-dimensional projective
space.
