@article{meland_2014,  title={Measurement of a cost function for US airlines: restricted and unrestricted translog models},  volume={8},  ISSN={2238-1031},  url={https://www.scielo.br/j/jtl/a/pXFTP97yxs88kSLmW5dh8py/},  number={2},  journal={Journal of Transport Literature},  publisher={Sociedade Brasileira de Planejamento dos Transportes},  author={Meland, William J.},  year={2014},  month={Apr},  pages={38–72} }