diff --git a/searx/engines/google.py b/searx/engines/google.py
index 1659a9a4..841212e0 100644
--- a/searx/engines/google.py
+++ b/searx/engines/google.py
@@ -134,42 +134,113 @@ spelling_suggestion_xpath = '//div[@class="med"]/p/a'
 
 
 def get_lang_info(params, lang_list, custom_aliases, supported_any_language):
-    ret_val = {}
+    """Composing various language properties for the google engines.
+
+    This function is called by the various google engines (google itself,
+    google-images, -news, -scholar, -videos).
+
+    :param dict param: request parameters of the engine
+
+    :param list lang_list: list of supported languages of the engine
+        :py:obj:`ENGINES_LANGUAGES[engine-name] <searx.data.ENGINES_LANGUAGES>`
+
+    :param dict lang_list: custom aliases for non standard language codes
+        (used when calling :py:func:`searx.utils.match_language)
+
+    :param bool supported_any_language: When a language is not specified, the
+        language interpretation is left up to Google to decide how the search
+        results should be delivered.  This argument is ``True`` for the google
+        engine and ``False`` for the other engines (google-images, -news,
+        -scholar, -videos).
+
+    :rtype: dict
+    :returns:
+        Py-Dictionary with the key/value pairs:
+
+        language:
+            Return value from :py:func:`searx.utils.match_language
+
+        country:
+            The country code (e.g. US, AT, CA, FR, DE ..)
+
+        subdomain:
+            Google subdomain :py:obj:`google_domains` that fits to the country
+            code.
+
+        params:
+            Py-Dictionary with additional request arguments (can be passed to
+            :py:func:`urllib.parse.urlencode`).
+
+        headers:
+            Py-Dictionary with additional HTTP headers (can be passed to
+            request's headers)
+    """
+    ret_val = {
+        'language' : None,
+        'country' : None,
+        'subdomain' : None,
+        'params' : {},
+        'headers' : {},
+    }
+
+    # language ...
 
     _lang = params['language']
     _any_language = _lang.lower() == 'all'
     if _any_language:
         _lang = 'en-US'
-
     language = match_language(_lang, lang_list, custom_aliases)
     ret_val['language'] = language
 
-    # the requested language from params (en, en-US, de, de-AT, fr, fr-CA, ...)
-    _l = _lang.split('-')
+    # country ...
 
-    # the country code (US, AT, CA)
+    _l = _lang.split('-')
     if len(_l) == 2:
         country = _l[1]
     else:
         country = _l[0].upper()
         if country == 'EN':
             country = 'US'
-
     ret_val['country'] = country
 
-    # the combination (en-US, en-EN, de-DE, de-AU, fr-FR, fr-FR)
-    lang_country = '%s-%s' % (language, country)
+    # subdomain ...
 
-    # subdomain
     ret_val['subdomain']  = 'www.' + google_domains.get(country.upper(), 'google.com')
 
-    ret_val['params'] = {}
-    ret_val['headers'] = {}
+    # params & headers
+
+    lang_country = '%s-%s' % (language, country)  # (en-US, en-EN, de-DE, de-AU, fr-FR ..)
+
+    # hl parameter:
+    #   https://developers.google.com/custom-search/docs/xml_results#hlsp The
+    # Interface Language:
+    #   https://developers.google.com/custom-search/docs/xml_results_appendices#interfaceLanguages
+
+    ret_val['params']['hl'] = lang_list.get(lang_country, language)
+
+    # lr parameter:
+    #   The lr (language restrict) parameter restricts search results to
+    #   documents written in a particular language.
+    #   https://developers.google.com/custom-search/docs/xml_results#lrsp
+    #   Language Collection Values:
+    #   https://developers.google.com/custom-search/docs/xml_results_appendices#languageCollections
 
     if _any_language and supported_any_language:
-        # based on whoogle
+
+        # interpretation is left up to Google (based on whoogle)
+        #
+        # - add parameter ``source=lnt``
+        # - don't use parameter ``lr``
+        # - don't add a ``Accept-Language`` HTTP header.
+
         ret_val['params']['source'] = 'lnt'
+
     else:
+
+        # restricts search results to documents written in a particular
+        # language.
+        ret_val['params']['lr'] = "lang_" + lang_list.get(lang_country, language)
+
         # Accept-Language: fr-CH, fr;q=0.8, en;q=0.6, *;q=0.5
         ret_val['headers']['Accept-Language'] = ','.join([
             lang_country,
@@ -178,18 +249,6 @@ def get_lang_info(params, lang_list, custom_aliases, supported_any_language):
             '*;q=0.5',
         ])
 
-        # lr parameter:
-        #   https://developers.google.com/custom-search/docs/xml_results#lrsp
-        # Language Collection Values:
-        #   https://developers.google.com/custom-search/docs/xml_results_appendices#languageCollections
-        ret_val['params']['lr'] = "lang_" + lang_list.get(lang_country, language)
-
-    ret_val['params']['hl'] = lang_list.get(lang_country, language)
-
-    # hl parameter:
-    #   https://developers.google.com/custom-search/docs/xml_results#hlsp The
-    # Interface Language:
-    #   https://developers.google.com/custom-search/docs/xml_results_appendices#interfaceLanguages
     return ret_val
 
 def detect_google_sorry(resp):
@@ -220,11 +279,8 @@ def request(query, params):
         query_url += '&' + urlencode({'tbs': 'qdr:' + time_range_dict[params['time_range']]})
     if params['safesearch']:
         query_url += '&' + urlencode({'safe': filter_mapping[params['safesearch']]})
-
-    logger.debug("query_url --> %s", query_url)
     params['url'] = query_url
 
-    logger.debug("HTTP header Accept-Language --> %s", lang_info.get('Accept-Language'))
     params['headers'].update(lang_info['headers'])
     params['headers']['Accept'] = (
         'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8'