APA   Click to copy
Chu, M., Diele, F., Plemmons, R., & Ragni, S. Optimality, computation and interpretation of nonnegative matrix factorizations. 2005. http://users.wfu.edu/plemmons/papers/chu_ple.pdf.

Chicago/Turabian   Click to copy
Chu, M, F Diele, R Plemmons, and S Ragni. Optimality, Computation and Interpretation of Nonnegative Matrix Factorizations. 2005. Http://Users.wfu.edu/Plemmons/Papers/chu_ple.Pdf, n.d.

MLA   Click to copy
Chu, M., et al. “Optimality, Computation and Interpretation of Nonnegative Matrix Factorizations. 2005.” Http://Users.wfu.edu/Plemmons/Papers/chu_ple.Pdf.

@techreport{chu-a,
  title = {Optimality, computation and interpretation of nonnegative matrix factorizations. 2005},
  journal = {http://users.wfu.edu/plemmons/papers/chu_ple.pdf},
  author = {Chu, M and Diele, F and Plemmons, R and Ragni, S}
}