Calculators & Reference
https://www.edx.org/course/subject/data-analysis-statistics
http://www.unconventionalstats.com/

http://www.calculator.net/
http://www.gapminder.org/
http://www.zanran.com/q/
https://tuvalabs.com/
http://htwins.net/scale2/

.    Mathematics   .

http://www.allaboutcircuits.com/tools/
http://www.mycarpentry.com/carpentry-calculators.html
http://www.printmini.com/calc.html