text: 
  
  // PDF //
  
  /**
  * @namespace pdf
  */
  var pdf = {
  		'version': '0.0.0' // semvar
  	};
  
  /**
  * METHOD: normal( mu, sigma )
  *	Returns a probability density function for a normal distribution with mean 'mu' and standard deviation 'sigma'.
  *
  * @param {number} mu - distribution mean
  * @param {number} sigma - distribution standard deviation
  * @returns {function} probability density function (PDF)
  */
  pdf.normal = function( mu, sigma ) {
  	var pi = Math.PI,
  		sqrt = Math.sqrt,
  		exp = Math.exp,
  		A = 1 / ( sigma * sqrt(2*pi) ),
  		B = -1 / ( 2 * sigma*sigma ),
  		C;
  	/**
  	* FUNCTION: normal( x )
  	*	Evaluates the probability distribution function for a normal distribution at input value 'x'.
  	*
  	* @param {number} x - input value
  	* @returns {number} evaluated PDF
  	*/
  	return function normal( x ) {
  		C = x - mu;
  		return A * exp( B * C * C );
  	};
  }; // end METHOD normal()