http://www.mathhelpforum.com/math-he...tml#post414469

However, there is a typo in the key there for

... the chain rule. Which should read, straight continuous lines differentiate downwards (integrate up) with respect to the main variable (in this case t), and the straight dashed line similarly but with respect to the dashed balloon expression (the inner function of the composite which is subject to the chain rule).