deletions | additions       diff --git a/section_Introduction_High_velocity_clouds__.tex b/section_Introduction_High_velocity_clouds__.tex  index b4318a2..b85dc0c 100644  --- a/section_Introduction_High_velocity_clouds__.tex  +++ b/section_Introduction_High_velocity_clouds__.tex 
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There are a number of indirect methods for measuring the distance to an HVC complex, including H$\alpha$ emission and kinematic structure \cite{Putman_2003, Peek_2007}, but the only proven direct distance measure is stellar absorption. By observing stars with measured distances at high spectral resolution, one can look for absorption lines in Na I, Ca II H & K, Ti II, and numerous ultraviolet absorption lines at the velocity of HI emission from HVCs \cite{1995A&A...302..364S}. By finding detections and non-detections of these absorption lines along lines of sight toward HI emitting HVCs, distances can be robustly measured. A number of clouds have well-measured distances using this method, but complex WD is not among them \cite{Wakker_2001, Wakker_2007, Thom_2008, Wakker_2008}.  In this work we report the first distance upper limit on Complex WD using medium resolution  absorption line spectroscopy toward a blue horizontal branch star. We extend the methods of \cite{Sirko_2004} to find the spectral type of a blue horizontal branch star, and thus put a precise distance limit. We use this to make some inferences as to the possible origin of Complex WD, and how it fits into the structure of Galactic HVCs as a whole.