(:notitlegroup:) 

   @article{cockrell2010,
    title     = {Calculating the Waveguide Invariant for Non-ideal Waveguides},
    author    = {Kevin L. Cockrell and Henrik Schmidt},
    journal   = {The Journal of the Acoustical Society of America},
    pages     = {1787-1787},
    number    = {3},
    volume    = {127},
    year      = {2010}}