Using graph search algorithms for a rigorous application of emergy algebra rules A. Marvuglia, B. Rugani, G. Rios, Y. Pigné, E. Benetto and L. Tiruta-Barna Rev. Metall., 110 1 (2013) 87-94 Published online: 13 March 2013 DOI: 10.1051/metal/2013050