particularly clear in the work of Kiselev [*at al.*]{} [@22] that the transition from hysteretic behaviour (as in Fig. \[fig5\](a)) to reversible behaviour with peaks in ${\rm d}V/{\rm
d}I$ occurs at the coercive field 600 Oe of the switching layer ($h_{\rm ext}=1$). The important point about the peaks in ${\rm
d}V/{\rm d}I$ is that for a given sign of $h_{\rm ext}$ they only occur for one sign of the bias. This clearly shows that this effect is due to spin-transfer and not to Oersted fields. Myers [*et al.*]{} [@25] show a current-field stability diagram similar to the bias-field one of Fig. \[fig4\] with a critical field of 1500 Oe. They examine the time dependence of the resistance at room temperature with the field and current adjusted so that the system is in the “both unstable” region in the fourth quadrant of Fig. \[fig4\] but very close to its top left-hand corner. They observe telegraph-noise-type switching between approximately P and AP states with slow switching times in the range 0.1-10 s. Similar telegraph noise with faster switching times was observed by Urazhdin [*et al.*]{} [@23] at current and field close to a peak in ${\rm
d}V/{\rm d}I$. In the region of 