Update README.md

Author: ramalho

02-array-seq/lispy/py3.9/README.md

@@ -7,7 +7,7 @@ _Luciano Ramalho_
 
 ## Major changes
 
-* Make the `lambda` form accept more than one expression as the body. This is consistent with _Scheme_ syntax, and provides a useful example for the book. To implement this:
+* Make the `lambda` form accept more than one expression as the body. This is consistent with [_Scheme_ syntax](https://web.mit.edu/scheme_v9.2/doc/mit-scheme-ref/Lambda-Expressions.html), and provides a useful example for the book. To implement this:
     * In `Procedure.__call__`: evaluate `self.body` as a list of expressions, instead of a single expression. Return the value of the last expression.
     * In `evaluate()`: when processing `lambda`, unpack expression into `(_, parms, *body)`, to accept a list of expressions as the body.
 * Remove the `global_env` global `dict`. It is only used as a default value for the `env` parameter in `evaluate()`, but it is unsafe to use mutable data structures as parameter default values. To implement this:
@@ -16,7 +16,7 @@ _Luciano Ramalho_
 * Rewrite the custom test script
 [lispytest.py](https://github.com/norvig/pytudes/blob/705c0a335c1811a203e79587d7d41865cf7f41c7/py/lispytest.py) as 
 [lis_test.py](https://github.com/fluentpython/example-code-2e/blob/master/02-array-seq/lispy/py3.9/lis_test.py):
-a standard [pytest](https://docs.pytest.org) test suite including new test cases, preserving all Norvig's the test cases for
+a standard [pytest](https://docs.pytest.org) test suite including new test cases, preserving all Norvig's test cases for
 [lis.py](https://github.com/norvig/pytudes/blob/705c0a335c1811a203e79587d7d41865cf7f41c7/py/lis.py)
 but removing the test cases for the features implemented only in
 [lispy.py](https://github.com/norvig/pytudes/blob/705c0a335c1811a203e79587d7d41865cf7f41c7/py/lispy.py)