The following formula is involved in the calculation of cash and cash equivalents to working capital ratios:

Cash & equivalents to working capital:
where C is a company's cash on hand, MMS is the amount of the company's market securities that will be maturing in 3 months or less, and WC is the company's working capital.

The following references can be used to cite this cash and cash equivalents to working capital calculator:
 Soper, D.S. (2017) "Cash and Cash Equivalents to Working Capital Calculator (Online Software)", http://www.danielsoper.com/fincalc. 
 Siegel, J. and Shim, J. (1997). "Schaum's Quick Guide to Business Formulas", New York, NY: McGrawHill. 