Write a bibliography about denoising

Gather information about denoising applied to ultrasound imaging.

Indicative due date : July 30th, 2017

Criteria to close the issue :

fork the repo
edit literature.bib with your references (.bib files can be handled for example with bibDesk on macOsX)
edit the file references/sigproc/Denoising.md with a summary of your findings. In this file you'll be able to cite references from literature.bib by calling : {{ "some-key" | cite }} where some-key has to be replaced by the cite key from literature.bib (you can inspire yourself from references/sigproc/IMGQ_metrics.md to understand how citations work)
if you use latex formulas, please put these between DOUBLE $$ : $$\sigma$$ for example
if you use latex formulas, please check the compatibility with the gitbook's plugin BEFORE making a pull request. A useful link for this : https://khan.github.io/KaTeX/
make a pull request refering to this issue

echopen / echopen_prototyping