Can't understand something about the convolutional networks gradient in TensorFlow
<p><a href="https://github.com/tensorflow/tensorflow/blob/r0.11/tensorflow/core/kernels/conv_grad_ops.cc#L171" rel="nofollow">Here</a> is the description about convolutional networks gradient in TensorFlow.</p>

<p>I don't know the meaning of <code>A' = a' * X^t</code>. I know <code>A'</code> stand for the  backprops. And <code>^t</code> is the Latex notation.</p>

<p>But <code>t</code> is undefined. So the point is the meaning of <code>X^t</code></p>