Preopen sets in bispaces
  The notion of preopen sets and precontinuity in a topological space was introduced by Mashhour et. al in 1982 [13]. Later the same was studied in a bitopological space in [7] and [9]. Here we have studied the idea of pairwise preopen sets (semi preopen) and pairwise precontinuity (semi precontinuity) in a more general structure of a bispace and investigate how far several results as valid in a bitopological space are affected in a bispace. 
Amar Kumar Banerjee and Pratap Kumar Saha
math.GN