Photospheric constraints, current uncertainties in models of stellar   atmospheres, and spectroscopic surveys
  We summarize here the discussions around photospheric constraints, current uncertainties in models of stellar atmospheres, and reports on ongoing spectroscopic surveys. Rather than a panorama of the state of the art, we chose to present a list of open questions that should be investigated in order to improve future analyses. 
Bertrand Plez and Nicolas Grevesse
astro-ph.SR