Jane Cleland-Huang Raffaella Settimi Xuchang Zou Peter Solc Automated classification of non-functional requirements. 103-120 2007 12 Requir. Eng. 2 http://dx.doi.org/10.1007/s00766-007-0045-1 db/journals/re/re12.html#Cleland-HuangSZS07