deletions | additions       diff --git a/3d_position.tex b/3d_position.tex  index ae1b952..1148fba 100644  --- a/3d_position.tex  +++ b/3d_position.tex 
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observations. If the sun had not been so placed, points in the mean  plane would not lie on the galactic equator.  \end{quotation}  In a further explanation of the IAU system in 1960, Blaauw et al. explain that stellar observations did, at that time, indicate the Sun to be at $z=22 \pm 2$ (22 pc above the plane), but the authors then discount those observations as too dangerously affected by hard-to-correct-for extinction in and near the Galactic Plane \citep{http://adsabs.harvard.edu/abs/1960MNRAS.121..123B}. \citep{1960MNRAS.121..123B}.  Instead, the 1959 IAU system relies on the 1950's measurements of HI, which showed the Sun to be at $z=4\pm 12$ pc off the Plane, consistent with the Sun being directly in the Plane ($z=0$). Interestingly, since the 1950's, the Milky Way's HI layer has been shown to have corrugations on the scale of 10's of pc \citep{Malhotra1995}, and there may be similar fluctuations in the mid-plane of the ${\rm H_2}$ \citep{Malhotra1994}, so it is still tricky to use gas measurements to determine the Sun's height off the plane. Astronomers today are still using the $(l^{II}, b^{II})$ Galactic coordinate system defined by  \citet{Blaauw1959}, but it is \emph{not} still the case, within observational uncertainty, that the