Uncertainty Propagation - http://lectureonline.cl.msu.edu/~mmp/labs/error/e2.htm, http://ipl.physics.harvard.edu/wp-uploads/2013/03/PS3_Error_Propagation_sp13.pdf, http://chemwiki.ucdavis.edu/Core/Analytical_Chemistry/Quantifying_Nature/Significant_Digits/Propagation_of_Error and http://www.rit.edu/~w-uphysi/uncertainties/Uncertaintiespart2.html.

SI Brochure - http://www.bipm.org/en/publications/si-brochure.

ISO/IEC 80000, International System of Quantities - https://en.wikipedia.org/wiki/ISO/IEC_80000.

JCGM-100:2008, Evaluation of measurement data — Guide to the expression of uncertainty in measurement - http://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf.

NIST SP811, Guide for the use of the International System of Units http://www.nist.gov/pml/pubs/sp811.