Bentham An Introduction chapter 4
The link address is: http://www.econlib.org/library/Bentham/bnthPML4.html#Chapter%20IV,%20Value%20of%20a%20Lot%20of%20Pleasure%20or%20Pain,%20How%20to%20be%20Measured
The link address is: http://www.econlib.org/library/Bentham/bnthPML4.html#Chapter%20IV,%20Value%20of%20a%20Lot%20of%20Pleasure%20or%20Pain,%20How%20to%20be%20Measured