diff --git a/cmd/lsf/main.go b/cmd/lsf/main.go
index 2a5f283..bce99ee 100644
--- a/cmd/lsf/main.go
+++ b/cmd/lsf/main.go
@@ -19,6 +19,7 @@ import (
 var (
 	sessionCache string
 	username     string
+	showGrades   bool
 )
 
 func init() {
@@ -29,6 +30,7 @@ func init() {
 	defaultCacheDir := path.Join(homeDir, ".cache/go-lsf/sessions")
 	flag.StringVar(&sessionCache, "session-cache", defaultCacheDir, "path where the session tokens are located")
 	flag.StringVar(&username, "username", "", "username to login with in lsf")
+	flag.BoolVar(&showGrades, "noten", false, "list grades")
 	flag.Parse()
 
 	err = os.MkdirAll(sessionCache, os.ModePerm)
@@ -51,7 +53,16 @@ func main() {
 		log.Fatal(err)
 	}
 
-	fmt.Printf("s: %+v\n", s)
+	if showGrades {
+		noten, err := s.Noten()
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Println("Noten:")
+		for _, note := range noten {
+			fmt.Println(note)
+		}
+	}
 }
 
 func readUsername() (string, error) {
@@ -69,7 +80,7 @@ func readPassword() (string, error) {
 	fmt.Print("Password: ")
 	b, err := terminal.ReadPassword(int(syscall.Stdin))
 	if err != nil {
-		return "", errors.Wrap(err, "could not read password")
+		return "", err
 	}
 	fmt.Print("\n")
 	password = string(b)
@@ -101,20 +112,16 @@ func session(username string) (*lsf.Session, error) {
 		return nil, errors.Wrapf(err, "could not read session file %s", sessionPath)
 	}
 	sid := strings.TrimSuffix(string(b), "\n")
-	s := &lsf.Session{
-		SID: sid,
-	}
-	valid, err := s.Valid()
-	if err != nil {
-		return nil, errors.Wrap(err, "could not check session")
-	}
-	if !valid {
-		fmt.Println("session is not valid")
+	s, err := lsf.NewSessionBySID(sid)
+	if err == lsf.ErrInvalSID {
+		log.Println("session is not valid")
 		err := os.Remove(sessionPath)
 		if err != nil {
 			log.Println(errors.Wrap(err, "could not remove invalid session file"))
 		}
 		return login(username)
+	} else if err != nil {
+		return nil, errors.Wrap(err, "could not get session by existing sid")
 	}
 	return s, nil
 }
@@ -122,7 +129,7 @@ func session(username string) (*lsf.Session, error) {
 func login(username string) (*lsf.Session, error) {
 	password, err := readPassword()
 	if err != nil {
-		return nil, errors.Wrap(err, "could not login")
+		return nil, errors.Wrap(err, "could not read password")
 	}
 	s, err := lsf.Login(username, password)
 	if err != nil {
diff --git a/module.go b/module.go
index 7c2c9e6..e4bbafd 100644
--- a/module.go
+++ b/module.go
@@ -1,5 +1,6 @@
 package lsf
 
+// Modul hold information about a module
 type Modul struct {
 	Nr int
 }
diff --git a/noten.go b/noten.go
index def852f..53afc87 100644
--- a/noten.go
+++ b/noten.go
@@ -1,10 +1,66 @@
 package lsf
 
 import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/PuerkitoBio/goquery"
 	"github.com/pkg/errors"
-	//"github.com/PuerkitoBio/goquery"
 )
 
-func (s *Session) Noten() (map[Modul]float32, error) {
-	return nil, errors.New("noten not implemented yet")
+// Note is a grade with associated data like the related module
+type Note struct {
+	Nr       string
+	Name     string
+	Semester string
+	Note     string
+	Status   string
+	CPs      string
+	Versuch  string
+}
+
+func (n *Note) String() string {
+	return fmt.Sprintf("%s: %s", n.Name, n.Note)
+}
+
+// Noten returns a list of the grades of all graded or signed up modules
+func (s *Session) Noten() ([]*Note, error) {
+	var noten []*Note
+	client := &http.Client{}
+	url := "https://lsf.hs-worms.de/qisserver/rds?state=notenspiegelStudent&next=list.vm&nextdir=qispos/notenspiegel/student&createInfos=Y&struct=auswahlBaum&nodeID=auswahlBaum%7Cabschluss%3Aabschl%3D05%2Cstgnr%3D1%7Cstudiengang%3Astg%3D938%2Cpversion%3D2018&expand=0&asi=" + s.ASI
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not prepare the request")
+	}
+	req.Header.Add("Cookie", fmt.Sprintf("JSESSIONID=%s", s.SID))
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not do the request")
+	}
+	doc, err := goquery.NewDocumentFromResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	// Find all tables. The last one contains the grades. Get all children rows.
+	rows := doc.Find("table").Last().Find("tr")
+	// The first three are the header, the average mark and a divider. So lets ignore them.
+	rows.Slice(3, rows.Length()).Each(func(_ int, row *goquery.Selection) {
+		vals := row.ChildrenFiltered("td").Map(func(i int, cell *goquery.Selection) string {
+			return strings.TrimSpace(cell.Text())
+		})
+		note := Note{
+			Nr:       vals[0],
+			Name:     vals[1],
+			Semester: vals[2],
+			Note:     vals[3],
+			Status:   vals[4],
+			CPs:      vals[5],
+			Versuch:  vals[7],
+		}
+		noten = append(noten, &note)
+	})
+
+	return noten, nil
 }
diff --git a/session.go b/session.go
index 68a8e1a..8d20942 100644
--- a/session.go
+++ b/session.go
@@ -5,17 +5,30 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 
 	"github.com/pkg/errors"
 )
 
+// Error variables
+var (
+	ErrInvalSID error = errors.New("invalid session id")
+)
+
+// Session contains the session id and whatever this obscure asi token is.
 type Session struct {
 	SID string
+	// ASI is a string you somehow have to pass to some endpoints.
+	ASI string
 }
 
+// Valid checks if the session id of the session is valid
 func (s *Session) Valid() (bool, error) {
 	client := &http.Client{}
+	// GET the logged in mail page.
+	// If correctly logged in there is a logout button.
+	// Otherwise there is a login button.
 	req, err := http.NewRequest("GET", "https://lsf.hs-worms.de/qisserver/rds?state=user&type=8&topitem=functions&breadCrumbSource=portal", nil)
 	if err != nil {
 		return false, errors.Wrap(err, "could not prepare the request")
@@ -39,6 +52,9 @@ func (s *Session) Valid() (bool, error) {
 	return false, errors.New("unexpected response body")
 }
 
+// Login tries to login with the given username and password.
+// If successful a new Session with the session id and asi
+// will be created and returned.
 func Login(username, password string) (*Session, error) {
 	client := &http.Client{
 		CheckRedirect: func(req *http.Request, via []*http.Request) error { // don't follow redirects
@@ -61,8 +77,13 @@ func Login(username, password string) (*Session, error) {
 	if resp.StatusCode == 302 {
 		for _, c := range resp.Cookies() {
 			if c.Name == "JSESSIONID" {
+				asi, err := asi(c.Value)
+				if err != nil {
+					return nil, errors.Wrap(err, "could not get asi")
+				}
 				return &Session{
 					SID: c.Value,
+					ASI: asi,
 				}, nil
 			}
 		}
@@ -73,3 +94,52 @@ func Login(username, password string) (*Session, error) {
 	}
 	return nil, errors.New("unexpected response status code")
 }
+
+// NewSessionBySID checks whether the given session id is valid and if so
+// a new Session with the session id and asi will be created and returned.
+func NewSessionBySID(sid string) (*Session, error) {
+	s := &Session{
+		SID: sid,
+	}
+	valid, err := s.Valid()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not check session")
+	}
+	if !valid {
+		return nil, ErrInvalSID
+	}
+	asi, err := asi(sid)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get asi")
+	}
+	return &Session{
+		SID: sid,
+		ASI: asi,
+	}, nil
+}
+
+func asi(sid string) (string, error) {
+	client := &http.Client{}
+	// GET Request with JESSIONID cookie to sitemap endpoint
+	req, err := http.NewRequest("GET", "https://lsf.hs-worms.de/qisserver/rds?state=sitemap&topitem=leer&breadCrumbSource=portal", nil)
+	if err != nil {
+		return "", errors.Wrap(err, "could not prepare the request")
+	}
+	req.Header.Add("Cookie", fmt.Sprintf("JSESSIONID=%s", sid))
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", errors.Wrap(err, "could not do the request")
+	}
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", errors.Wrap(err, "could not read the response body")
+	}
+	// The asi is in some links as GET parameter.
+	// Filter it with regexp
+	re := regexp.MustCompile(`asi=([^"]+)`)
+	match := re.FindSubmatch(b)
+	if len(match) != 2 {
+		return "", errors.New("no asi found")
+	}
+	return string(match[1]), nil
+}