Aguado J, Campbell A, Ascaso C, Navarro P, Garcia-Esteve L, Luciano JV. Examining the factor structure and discriminant validity of the 12-Item General Health Questionnaire (GHQ-12) among Spanish postpartum women. Assessment. 2012 Dec 19;19(4):517-25.
Edwards PET, Parsons GR, Myers KH. The economic value of viewing migratory shorebirds on the Delaware Bay: an application of the single-site travel cost model using on-site data. Hum Dimens Wildl. 2011;16(6):435-44. doi: 10.1080/10871209.2011.608180