According to the observation on 2008/3/11, what was the height of Elly Koss?
2008/3/11 refers to date = '2008-03-11'; height refers to DESCRIPTION = 'Body Height' from observations;
SELECT T2.value, T2.units FROM patients AS T1 INNER JOIN observations AS T2 ON T1.patient = T2.PATIENT WHERE T1.first = 'Elly' AND T1.last = 'Koss' AND T2.date = '2008-03-11' AND T2.description = 'Body Height'