How did stern help schindler?

Oskar Schindler was a German businessman who saved the lives of more than a thousand mostly Polish-Jewish refugees during the Holocaust by employing them in his enamelware and munitions factories in occupied Poland and the Protectorate of Bohemia and Moravia. It is estimated that Schindler saved at least 6,000 Jews from certain death in Nazi concentration camps.

I could not find any historical accounts of a person named "stern" who directly played a role in helping Oskar Schindler in his endeavors to protect Jewish individuals during the Holocaust.