diff --git a/.travis.yml b/.travis.yml
index 9b50d47..75538cb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -40,9 +40,12 @@ env:
 
 python:
   - "2.7"
-  - "3.3"
-  - "3.4"
   - "3.5"
+  - "pypy"
+
+matrix:
+  allow_failures:
+    - python: pypy
 
 before_install:
   - "travis_retry pip install --upgrade pip setuptools py"
diff --git a/docs/conf.py b/docs/conf.py
index 04236cc..632824a 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -137,8 +137,8 @@
     'github_banner': True,
     'show_powered_by': False,
     'extra_nav_links': {
-        'invenio-csl-rest@GitHub': 'http://github.com/inveniosoftware/invenio-csl-rest',
-        'invenio-csl-rest@PyPI': 'http://pypi.python.org/pypi/invenio-csl-rest/',
+        'invenio-csl-rest@GitHub': 'https://github.com/inveniosoftware/invenio-csl-rest',
+        'invenio-csl-rest@PyPI': 'https://pypi.python.org/pypi/invenio-csl-rest/',
     }
 }
 
@@ -329,3 +329,6 @@
 
 # Example configuration for intersphinx: refer to the Python standard library.
 intersphinx_mapping = {'https://docs.python.org/': None}
+
+# Autodoc configuraton.
+autoclass_content = 'both'
diff --git a/setup.py b/setup.py
index 385634b..377152a 100644
--- a/setup.py
+++ b/setup.py
@@ -59,6 +59,7 @@
 ]
 
 install_requires = [
+    'Flask>=0.11.1',
     'citeproc-py-styles>=0.1.0',
     'invenio-rest>=1.0.0a9',
 ]
@@ -112,9 +113,9 @@
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
-        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: Implementation :: CPython',
+        'Programming Language :: Python :: Implementation :: PyPy',
         'Development Status :: 1 - Planning',
     ],
 )