@article{SINNHUBER14_M_ACP,
   author = "M. Sinnhuber and B. Funke and T. von Clarmann and
             M. L{\'o}pez-Puertas and G. P. Stiller and A. Sepp{\"a}l{\"a}",
   title  = "Variability of NO$_x$ in the polar middle atmosphere from
             {O}ctober 2003 to {M}arch 2004: vertical transport vs.
             local production by energetic particles",
   journal= "Atmos. Chem. Phys.",
   volume = "14",
   number = "14",
   pages  = "7681-7692",
   doi    = "10.5194/acpd-14-7681-2014",
   year   = "2014"   }