- http://blog.cloudfour.com/responsive-guide-to-type-sizing/ - author's tl;dr: "1) Use a modular scale to define your typographic proportions. 2) Create a scale that is flexible enough to work on many screen sizes. 3) Use higher steps from your scale when more proportional contrast is needed. 4) Don’t limit the use of your scale to specific elements." I would also add: 5) Take care about line-height of wrapped headings 6) For implementing the scale use calc (https://github.com/postcss) or define Sass variables with your sizes
- http://tympanus.net/codrops/2013/11/19/techniques-for-responsive-typography/ - awesome tricks with font legibility. "It’s best that you use some kind of CSS reset when you define styles for your fonts, because browsers have predefined margins for headings and paragraphs that may interfere with the space you want to define between your lines.", "In order to set the font sizes in em, there’s a simple rule to follow to determine the em alternative to a pixel value. Ethan Marcotte’s article on the Typekit blog explains how to calculate the font sizes in em clearly, so be sure to give it a read if you’re not familiar with it.". Start using @media (luminosity: [normal, dim, washed]).
- https://css-tricks.com/viewport-sized-typography/ - I am not sure about this one being perfect solution.