How many years after the prisoners from the Czech Legion of the Austro-Hungarian army were released were German prisoners still being held for?
return the  prisoners  from  the   Czech Legion of the Austro-Hungarian army were released ;return German prisoners  were still being held ;return year of #1 ;return year of #2 ;return difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']