has yet detected a signal, but many have placed interesting upper limits on possible sources. These searches have generally been drawn from one of three types.

Targeted searches are aimed at a single known pulsar, with a known precise timing solution. The first search for continuous waves, using data from , was of this type [@S1pulsar], and subsequent searches have probed the Crab and Vela pulsars, among others [@S2pulsars; @S3S4pulsars; @S5Crab; @VirgoVela; @S5pulsars; @S6pulsars]. A number of these most recent searches have been able to set direct upper limits on emission comparable to or stricter than the indirect “spin-down limits” (derived from energy conservation, as well as the distance from Earth of the target, its gravitational-wave frequency, and the frequency’s first derivative, the “spin-down”) for a few of the pulsars searched.

All-sky searches, as their name suggests, survey the entire sky for neutron stars not seen as pulsars. These are very computationally costly, searching over wide frequency bands and covering large ranges of spin-down parameters [@S2Hough; @S2Fstat; @S4PSH; @S4Einstein; @S5PowerFlux; @S5Einstein; @S5PowerFlux2; @S5Einstein2; @S5Hough; @VirgoAllSky]. The latest of these have incorporated new techniques to cover possible binary parameters as well [@AllSkyBinary]. Recent all-sky searches have set direct upper limits close 