Here is a post at my blog. The Damodaran post you referenced in an earlier comment was my jumping off point.

http://idiosyncraticwhisk.blogspot.com/2014/10/evidence-is-optional-for…

Here is a slide from JP Morgan on leverage (slide number 6):

http://www.businessinsider.com/jp-morgan-q4-guide-to-the-markets-2014-1…

Here is one of my posts discussing corporate leverage and interest rates, although the topic is admittedly speculative and contrarian:

http://idiosyncraticwhisk.blogspot.com/2014/06/risk-valuations-part-3-l…