"Crab Pulsar" . . "Crab Nebula pulsar" . . "PSR B0531+21" . "pulsar in the Crab nebula" . "Crab nebula pulsar" . . . "Crab pulsar" . "Pulsar" . "Crab-like pulsar" . . . "Crab" . . . "Crab Pulsar" . .