[Source](https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.phdcompletion.org/resources/cgsnsf2008_sowell.pdf&ved=0ahUKEwj95P_2gb3MAhUM2R4KHRa2CCoQFggmMAM&usg=AFQjCNHLz0J1rbC2A1ajmb3R3igIp0BIcg&sig2=io81cXVUh7Fq9pa96YDe8g "Permalink to ")