message: Update LSTM paper reference
  Match
diff: @@ -97,10 +97,10 @@ class CoupledInputForgetGateLSTMCell(rnn_cell_impl.RNNCell):
  The default non-peephole implementation is based on:
  - http://www.bioinf.jku.at/publications/older/2604.pdf
  + https://pdfs.semanticscholar.org/1154/0131eae85b2e11d53df7f1360eeb6476e7f4.pdf
  - S. Hochreiter and J. Schmidhuber.
  - "Long Short-Term Memory". Neural Computation, 9(8):1735-1780, 1997.
  + Felix Gers, Jurgen Schmidhuber, and Fred Cummins.
  + "Learning to forget: Continual prediction with LSTM." IET, 850-855, 1999.
  The peephole implementation is based on:
  @@ -2448,10 +2448,10 @@ class LayerNormLSTMCell(rnn_cell_impl.RNNCell):
  The default non-peephole implementation is based on:
  - http://www.bioinf.jku.at/publications/older/2604.pdf
  + https://pdfs.semanticscholar.org/1154/0131eae85b2e11d53df7f1360eeb6476e7f4.pdf
  - S. Hochreiter and J. Schmidhuber.
  - "Long Short-Term Memory". Neural Computation, 9(8):1735-1780, 1997.
  + Felix Gers, Jurgen Schmidhuber, and Fred Cummins.
  + "Learning to forget: Continual prediction with LSTM." IET, 850-855, 1999.
  The peephole implementation is based on:
  @@ -2802,9 +2802,11 @@ class WeightNormLSTMCell(rnn_cell_impl.RNNCell):
  Training of Deep Neural Networks
  The default LSTM implementation based on:
  - http://www.bioinf.jku.at/publications/older/2604.pdf
  - S. Hochreiter and J. Schmidhuber.
  - "Long Short-Term Memory". Neural Computation, 9(8):1735-1780, 1997.
  +
  + https://pdfs.semanticscholar.org/1154/0131eae85b2e11d53df7f1360eeb6476e7f4.pdf
  +
  + Felix Gers, Jurgen Schmidhuber, and Fred Cummins.
  + "Learning to forget: Continual prediction with LSTM." IET, 850-855, 1999.
  The class uses optional peephole connections, optional cell clipping
  and an optional projection layer.
  