Walker, Helen and Brammer, Stephen. (2012) The relationship between sustainable procurement and e-procurement in the public sector. International Journal of Production Economics, Vol.140 (No.1). pp. 256-268. ISSN 0925-5273

Schotanus, Fredo, Bakker, Elmer, Walker, Helen and Essig, Michael. (2011) Development of purchasing groups during their life cycle : from infancy to maturity. Public Administration Review, Vol.71 (No.2). pp. 265-275. ISSN 0033-3352

Brammer, Stephen and Walker, Helen. (2011) Sustainable procurement in the public sector : an international comparative study. International Journal of Operations & Production Management, Vol.31 (No.4). pp. 452-476. ISSN 0144-3577

Walker, Helen and Brammer, Stephen. (2009) Sustainable procurement in the United Kingdom public sector. Supply Chain Management: An International Journal, Vol.14 (No.2). pp. 128-137. ISSN 1359-8546