st: AW: re: panel re vs. fe model

["Thomas Erdmann" <tom.erdmann@web.de>]

Mark, thanks again for the further clarification.

Kit, Jason, in saying that I address time- and firm effects I omitted
"biasing SEs". 

A reference which I used to learn about this is: 
Petersen, 2006. Estimating Standard Errors in Finance Panel Data Sets:
Comparing Approaches, Working paper.
http://www.kellogg.northwestern.edu/faculty/petersen/htm/working.htm