The notion of basic net (called also basic polyhedron) on S2 plays a
central role in Conway's approach to enumeration of knots and links in S3.
Drobotukhina applied this approach for links in RP3 using basic nets on
RP2. By a result of Nakamoto, all basic nets on S2 can be obtained from a
very explicit family of minimal basic nets (the nets (2×n)∗, n≥3,
in Conway's notation) by two local transformations. We prove a similar result
for basic nets in RP2.
We prove also that a graph on RP2 is uniquely determined by its pull-back
on S3 (the proof is based on Lefschetz fix point theorem).Comment: 14 pages, 15 figure