Biembeddings of 2-Rotational Steiner Triple Systems
				
										Keywords:
				
				
																		Topological embedding, 													Steiner triple system, 													Heffter difference set															
			
			
										Abstract
It is shown that for $v\equiv 1$ or 3 (mod 6), every pair of Heffter difference sets modulo $v$ gives rise to a biembedding of two 2-rotational Steiner triple systems of order $2v+1$ in a nonorientable surface.