Keep fonts optimized
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Set should be as minimum as possible 
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Fallback on smaller fontset / standart fontset on mobile devices 
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woff2fonts types for progressive browser (Chrome, Opera, Android)
 Converter: https://everythingfonts.com/woff-to-woff2
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Gzip ttf,eof,svgfonts for old browsers,woff&woff2are already optimized
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Put most usage font loading in html: 
 CSS request containing your font-face definition should not block page render.
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Included fonts should be limited in minimum languages. For example by including from Google-Fonts, we need to get only latin coding. 
Useful links
https://css-tricks.com/snippets/css/using-font-face/
http://blog.typekit.com/2013/04/17/fallback-fonts-on-mobile-devices/
https://www.igvita.com/2014/01/31/optimizing-web-font-rendering-performance/
https://www.igvita.com/2012/09/12/web-fonts-performance-making-pretty-fast/#optimizing
https://www.filamentgroup.com/lab/font-loading.html
https://www.filamentgroup.com/lab/font-events.html