message: change format of references
  change format of references
diff: @@ -32,16 +32,13 @@ class Adam(optimizer_v2.OptimizerV2):
  """Optimizer that implements the Adam algorithm.
  Adam optimization is a stochastic gradient descent method that is based on
  - adaptive estimation of first-order and second-order moments. According to the
  - reference, the method is 'computationally efficient, has little memory
  + adaptive estimation of first-order and second-order moments. According to the paper
  + [Adam: A Method for Stochastic Optimization. Kingma et al., 2014](http://arxiv.org/abs/1412.6980),
  + the method is "*computationally efficient, has little memory
  requirement, invariant to diagonal rescaling of gradients, and is well suited
  - for problems that are large in terms of data/parameters'.
  + for problems that are large in terms of data/parameters*".
  - # References
  - See [Kingma et al., 2014](http://arxiv.org/abs/1412.6980)
  - ([pdf](http://arxiv.org/pdf/1412.6980.pdf)).
  - For AMSGrad see [Reddi et al., 2-18]
  - (https://openreview.net/pdf?id=ryQu7f-RZ)
  + For AMSGrad see [On The Convergence Of Adam And Beyond. Reddi et al., 5-8](https://openreview.net/pdf?id=ryQu7f-RZ).
  """
  def __init__(self,
  