Martin Lefley Martin J. Shepperd Using Genetic Programming to Improve Software Effort Estimation Based on General Data Sets. 2477-2487 2003 conf/gecco/2003-2 GECCO http://link.springer.de/link/service/series/0558/bibs/2724/27242477.htm db/conf/gecco/gecco2003-2.html#LefleyS03