Changed the stamtement to indicate that only wf(u)\wf(f) (rather than all of wf(u)) is invariant under the bicharacteristic flow, as stated in the cited source by Duistermaat and HÃ¶rmander.

Anonymous

]]>I filled in the previously missing definitions of the technical assumptions of the theorem (here), also gave them their own stand-alone entries: proper support and symbol order of pseudo-differential operators.

]]>started something at *propagation of singularities theorem*