Temporal coherence of MgO-based magnetic tunnel junction spin torque oscillators, Houssameddine, D., Ebels, U., Dieny, B., Garello, K., Michel, J.-P., Vincent, P., Delaët, B., Cyrille, M.-C., Katine, J.A., Florez, S.H., Mauri, D., Zeltser, A., Ozatay, O., Folks, L., Terris, B.D., Physical Review Letters, 102, 257202 (2009)