Correct sentence-case on link and correct a typo (#1939)

doc/sphinx/source/howto/update.rst

@@ -44,7 +44,7 @@ In working with nGraph-based construction of graphs, updating takes
 the same approach. During training, we include all the weights as 
 arguments to the training function and return the updated weights 
 along with any other results. For more complex forms of training, 
-such as those using momentum, we would add the momementum tensors 
+such as those using momentum, we would add the momentum tensors 
 as additional arguments and include their updated values as additional 
 results. A simple case is illustrated in the documentation for how 
 to :doc:`derive-for-training`.

doc/sphinx/source/project/about.rst

@@ -72,7 +72,7 @@ The *nGraph core* uses a **strongly-typed and platform-neutral stateless graph
 representation** for computations. Each node, or *op*, in the graph corresponds
 to one :term:`step` in a computation, where each step produces zero or more 
 tensor outputs from zero or more tensor inputs. For a more detailed dive into 
-how this works, read our documentation on how to :doc:`../howto/execute`.
+how this works, read some of our :doc:`how to <../howto/execute>` articles.
 
 
 .. _framework-flexibility: