“…The earliest references we are aware of is [13], followed by [25,52,3,4]. Inspired by the work on invariant measures for the Benjamin-Ono equation [10,48,49,50], quasi-invariance of Gaussian measure for several dispersive models was obtained in recent years, see [9,14,16,11,12,18,31,34,35,36,37,39,43,47]. The method to identify the densities in Theorem 1.3 is inspired by recent works [9,15].…”