《北史·列传·卷四》
后来灵太后曾经对左右侍臣们说： 刘腾、元叉以前曾经向我索要铁券，希望能够免除死罪，我故意拖着不给他。 
其后灵太后顾谓侍臣曰： 刘腾、元叉昔邀朕索铁券，望得不死，朕赖不与。 
Later, Empress Ling once said to the left and right attendants: Liu Teng and Yuancha had once asked me for iron coupons, hoping to be exempted from the death penalty. I deliberately delayed and did not give them.