I'm doing a literature survey on high quality oscillators, and since this is peripheral to my area of specialization, I'd appreciate some help. I'm looking for a low frequency oscillator (~10Hz and up) with a frequency stability of about 30ppm/C, amplitude stability of about 3ppm/C and low harmonic distortion (all higher harmonics at least 90dB below fundamental). Is anyone aware of anything in the market or in literature that has the above specs? If you know of something that comes close, please tell me where to look it up. And if you are not aware of anything that's been built with these specs, I'd like to hear about that too (and any related wisdom) - negative responses are valuable as well.