1. Microsoft project oxford emotion api. https://www.projectoxford.ai/emotion. Microsoft project oxford emotion api. https://www.projectoxford.ai/emotion.
2. Noise robust differentiators for second derivative estimation. http://www.holoborodko.com/pavel/downloads/NoiseRobustSecondDerivative. Noise robust differentiators for second derivative estimation. http://www.holoborodko.com/pavel/downloads/NoiseRobustSecondDerivative.
3. Heart rate variability: a review;Acharya U.R.;Medical and Biological Engineering and Computing,2006
4. See through walls with WiFi!