Include \usepackage{color,hyperref} with Preamble for clickable link in blue. Compile with pdflatex. @article{WK:RM, author = {Weil, Roman L. and Paul Carlisle Kettler}, title = {Rearranging matrices to block-angular form for decomposition (and other) algorithms}, note = {\textcolor{blue}{\url{www.paulcarlislekettler.net/docs/Weil_Kettler.pdf}}}, journal = {Manag. Sci. 1 (Theory Series)}, year = {1971}, volume = {18}, number = {}, pages = {98-108}}