diff --git a/README.rst b/README.rst
index 9ffa19e..edd7efc 100644
--- a/README.rst
+++ b/README.rst
@@ -213,6 +213,10 @@ To use the extensions below you must import from `jsonpath_ng.ext`.
 +==============+===============================================+
 | len          | - ``$.objects.`len```                         |
 +--------------+-----------------------------------------------+
+| keys         | - ``$.objects.`keys```                        |
++--------------+-----------------------------------------------+
+| str          | - ``$.field.`str()```                         |
++--------------+-----------------------------------------------+
 | sub          | - ``$.field.`sub(/foo\\\\+(.*)/, \\\\1)```    |
 |              | - ``$.field.`sub(/regex/, replacement)```     |
 +--------------+-----------------------------------------------+
diff --git a/tests/test_examples.py b/tests/test_examples.py
index ca2ec17..c07732a 100644
--- a/tests/test_examples.py
+++ b/tests/test_examples.py
@@ -37,9 +37,15 @@
         ("$..book[-1:]", Child(Descendants(Root(), Fields("book")), Slice(start=-1))),
         #
         # The first two books
-        # "$..book[0,1]"  # Not implemented
+        ("$..book[0,1]", Child(Descendants(Root(), Fields("book")), Index(0,1))),
         ("$..book[:2]", Child(Descendants(Root(), Fields("book")), Slice(end=2))),
         #
+        # Categories and authors of all books
+        (
+            "$..book[0][category,author]", 
+            Child(Child(Descendants(Root(), Fields('book')), Index(0)), Fields('category','author')),
+        ),
+        #
         # Filter all books with an ISBN
         (
             "$..book[?(@.isbn)]",