{HEAD ~ The discharge vessel} encloses a discharge space having an ionizable filling which, in addition to Hg, contains a quantity of iodide of Na, {TAIL ~ Tl}, Ho and Ca 
{ HEAD ~ The discharge vessel } encloses a discharge space having an ionizable filling which , in addition to Hg , contains a quantity of iodide of Na , { TAIL ~ Tl } , Ho and Ca
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH