SIMBAD references

We present a study of single pulses from nine bright northern pulsars to investigate the behaviour of circular polarization, V. The observations were conducted with the Effelsberg 100-m radio telescope at 1.41 and 4.85 GHz and the Westerbork radio telescope at 352 MHz. For the first time, we present the average profile of the absolute circular polarization {verbar}V {verbar} in the single pulses. We demonstrate that the average profile of {verbar}V {verbar} is the distinguishing feature between pulse components that exhibit low V in the single pulses and components that exhibit high V of either handedness, despite both cases resulting in a low mean. We also show that the {verbar}V {verbar} average profile remains virtually constant with frequency, which is not generally the case for V, leading us to the conclusion that {verbar}V {verbar} is a key quantity in the pulsar emission problem.