diff --git a/ddapioper.py b/ddapioper.py
index 4b1dd66..0737311 100644
--- a/ddapioper.py
+++ b/ddapioper.py
@@ -1,5 +1,14 @@
 """Module to connect to the dd-api-oper
 
+This module contains the following classes:
+
+ * ddApiOper: Main class to connect to the dd api oper interface
+ * ddApiResult: Super class for results
+   - ddApiLocation: Result class for locations
+   - ddApiQuantitie: Result class for quantities
+   - ddApiValues: Result class for values
+ * ddApiOperHttpError: Exception class for http errors
+
 See:
     https://digitaledeltaorg.github.io/dd-oper.v201.html
 """
@@ -22,6 +31,17 @@ class ddApiOper:
     RWS_DD_API = "https://ddapi.rws.nl/dd-oper/2.0"
 
     def __init__(self, certfile=None, certkey=None, url=RWS_DD_API, checkssl=True):
+        """ddApiOper(certfile, certKey, url="https://ddapi.rws.nl/dd-oper/2.0", checkssl=True)
+
+certfile:           x509 pki overheidscertificaat
+certKey:            Unencrypted private key
+url(optional):      dd Api url (default https://ddapi.rws.nl/dd-oper/2.0)
+checkssl(optional): Check ssl keychain (default true)
+
+Details for the certificate files see:
+    https://requests.readthedocs.io/en/master/user/advanced/#client-side-certificates
+
+"""
         self.certfile = certfile
         self.certkey  = certkey
         self.url      = url
@@ -29,6 +49,12 @@ class ddApiOper:
         logging.debug("ddApiOper.__init__(%s)" % url)
 
     def get(self, url):
+        """get(url)
+
+Get the json data from the dd-api with pyton request.
+
+Note: Internal use!
+"""
         logging.debug("ddApiOper.get(%s)" % url)
         try:
             req = requests.get(url, cert=(self.certfile, self.certkey))
@@ -40,17 +66,44 @@ class ddApiOper:
         return(req.json())
 
     def locations(self):
+        """locations()
+
+Request the list of locations and return a ddApiLocation object.
+"""
         return(ddApiLocation(self.get(self.url + "/locations")["results"]))
 
     def quantities(self):
+        """quantities()
+
+Request the list of quantities and return a ddApiQuntitie object.
+"""
         return(ddApiQuantitie(self.get(self.url + "/quantities")["results"]))
 
     def location_quantities(self, location):
+        """location_quantities(location)
+
+location: A dd-api location (e.g. hoekvanholland)
+
+Request the list of quantities from a location and return
+a ddApiQuntitie object.
+"""
         return(ddApiQuantitie(self.get(self.url + "/locations/%s/quantities" % location)["results"]))
 
     def values(self, location, quantitie, process="measurement",
                      starttime=None, endtime=None,
                      intervalLength="10min", aspectset="minimum"):
+        """values(location, quantitie, process="measurement",
+    starttime=None, endtime=None, intervalLength="10min", aspectset="minimum")
+
+location:                 A dd-api location (e.g. hoekvanholland)
+quantitie:                A dd-api quantitie (e.g. waterlevel)
+process(optional):        Default measurement (forecast, astronomical, advise)
+starttime(optional):      Start of the time serie (Default 24 hours ago)
+endtime(optional):        End of the time serie (Default now)
+intervalLength(optional): Interval between measurements (default 10 min)
+aspectset(optional):      Default minimum (normal, maximum)
+
+"""
         if not endtime:
             endtime = datetime.utcnow()
         if not starttime:
@@ -77,16 +130,32 @@ class ddApiOper:
                         ))))
 
 class ddApiResult(object):
+    """
+Class ddApiResult:
+
+Base class for ddApiResults.
+"""
 
     def __init__(self, data):
+        """ddApiResult(data)"""
         self.data = data
 
 class ddApiLocation(ddApiResult):
+    """
+Class ddApiLocation:
+
+ddApi Result class for locations.
+"""
+
     def __init__(self, data):
         super().__init__(data)
         self.createIndex()
 
     def createIndex(self):
+        """createIndex()
+
+Note: Internal function
+"""
         self.__index = {}
         i = 0
         for loc in self.data:
@@ -94,45 +163,109 @@ class ddApiLocation(ddApiResult):
             i+=1
 
     def locationNames(self):
+        """locationNames()
+
+Returns a list of ddapi location names
+"""
         return(self.__index.keys())
          
     def locationDetail(self, locationName):
+        """locationDetail(locationName):
+
+Returns the detais of a location from the list
+"""
         return(self.data[self.__index[locationName]])
 
     def displayNameGlobal(self, locationName):
+        """displayNameGlobal(locationName)
+
+Returns the global display name of a location
+"""
         return(self.locationDetail(locationName)["properties"]["displayNameGlobal"])
 
     def coordinate(self, locationName):
+        """coordinate(locationName)
+
+Returns the coordinates of a location
+"""
         return(self.locationDetail(locationName)["geometry"]["coordinates"])
 
 class ddApiQuantitie(ddApiResult):
+    """
+Class ddApiQuantitie:
+
+ddApi Result class for Quantities.
+"""
 
     def quantities(self):
+        """quantities()
+
+Returns a list of quantities
+"""
         return(self.data)
 
 class ddApiValues(ddApiResult):
+    """
+Class ddApiValues:
+
+ddApi Result class for values.
+"""
 
     def provider(self):
+        """provider()
+
+Returns the provider metadata.
+"""
         return(self.data["provider"])
 
     def result(self, index=0):
-        return(self.data["results"][0])
+        """result(index=0)
+
+Returns the results part of the response.
+"""
+        return(self.data["results"][index])
 
     def aspectSet(self):
+        """aspectSet()
+
+Returns the metadata of the aspectSet
+"""
         return(self.result()["observationType"]["aspectSet"]["aspects"])
 
     def location(self):
+        """location()
+
+Returns the location metadata
+"""
         return(self.result()["location"])
 
     def source(self):
+        """source()
+
+Returns the source metadata
+"""
         return(self.result()["source"])
 
     def values(self, index=0):
-# pprint(v1.data["results"][0]["events"][0]["aspects"][0]["points"][0]["value"])
+        """values(index=0)
+
+Returns the values at ittorator of tupples.
+
+ (time, value)
+ (time, value)
+
+Note:
+  Is this the correct return data format??
+  This may change!
+"""
         for e in self.result()["events"]:
             yield (e["timeStamp"], e["aspects"][index]["points"][0]["value"])
 
     def sip(self, index=0):
+        """sip(index)
+
+Returns the result set as string in the sip format!
+"""
         r   = "!"
         sep = " "
         for e in self.result()["events"]:
@@ -142,8 +275,12 @@ class ddApiValues(ddApiResult):
             sep = ";"
         return(r)
         
-        
 class ddApiOperHttpError(Exception):
+    """
+Class ddApiOperHttpError
+
+Exception class to use on http errors.
+"""
     def __init__(self, code):
         self.code = code