diff --git a/code/.gitignore b/code/.gitignore
index eb7228e..4a71f7f 100644
--- a/code/.gitignore
+++ b/code/.gitignore
@@ -10,3 +10,4 @@
 !/aussagenlogik
 !/utests
 !/**/*.py
+!/*/*.lark
diff --git a/code/aussagenlogik/grammar.lark b/code/aussagenlogik/grammar.lark
new file mode 100644
index 0000000..6f29415
--- /dev/null
+++ b/code/aussagenlogik/grammar.lark
@@ -0,0 +1,37 @@
+%import common.WS
+%import common.NUMBER
+%import common.WORD
+
+%ignore WS
+
+// Schemata für Ausdrücke
+// 'open'   = äußerste Klammern fehlen, wenn nötig.
+// 'closed' = sonst
+?expr:   open | closed
+?closed: atomic | not | "(" open ")"
+?open:   and | and_long | or | or_long | impl
+
+// Schemata für atomische Ausdrücke
+?atomic:  false | true | atom | generic
+?false:   /0|false/                         -> kontr
+?true:    /1|true/                          -> taut
+?atom:    /A[0-9]+/                         -> atom
+// als 'generischen' Formeln schreibe bspw. {F}, {G}, {F1}, usw.
+?generic: "{" /((?!({|})).)+/ "}"           -> beliebig
+
+// Symbole (erlaube mehrere Varianten)
+?symb_not:  /!|~|not/                       -> symb
+?symb_and:  /&+|\^|and/                     -> symb
+?symb_or:   /\|+|v|or/                      -> symb
+?symb_impl: /->|=>/                         -> symb
+
+// Schema für Negation: ¬ F
+?not:                 symb_not  closed      -> neg
+// Schemata für Konjunktion: F1 ⋀ F2 bzw. F1 ⋀ F2 ⋀ ... ⋀ Fn
+?and:        closed   symb_and  closed      -> konj
+?and_long: [ closed ( symb_and  closed )+ ] -> konj_lang
+// Schemata für Disjunktion: F1 ⋁ F2 bzw. F1 ⋁ F2 ⋁ ... ⋁ Fn
+?or:         closed   symb_or   closed      -> disj
+?or_long:  [ closed ( symb_or   closed )+ ] -> disj_lang
+// Schema für Implikation: F1 ⟶ F2
+?impl:       closed   symb_impl closed      -> impl
diff --git a/code/aussagenlogik/schema.py b/code/aussagenlogik/schema.py
index da4b829..778890b 100644
--- a/code/aussagenlogik/schema.py
+++ b/code/aussagenlogik/schema.py
@@ -18,42 +18,9 @@ from typing import Union;
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ## lexer
-lexerAussagenlogik = Lark(
-    '''
-    %import common.WS
-    %import common.NUMBER
-    %import common.WORD
-    %ignore WS
-
-    ?start: expr | open
-
-    ?expr:     atomic | not | closed
-    ?open:     and | and_long | or | or_long | impl
-    ?closed:   "(" open ")"
-
-    // atomische Ausdrücke
-    ?atomic:    false | true | atom | generic
-    ?false:     "0"                     -> kontr
-    ?true:      "1"                     -> taut
-    ?atom:      /A[0-9]+/               -> atom
-    ?generic:   "{" /((?!({|})).)+/ "}" -> beliebig
-
-    // Symbole
-    ?symb_not:  /!/     -> symb
-    ?symb_and:  /&+/    -> symb
-    ?symb_or:   /\\|+/  -> symb
-    ?symb_impl: /->|=>/ -> symb
-
-    // Junktoren
-    ?not:               symb_not   expr      -> neg
-    ?and:        expr   symb_and   expr      -> konj
-    ?and_long: [ expr ( symb_and   expr )+ ] -> konj_lang
-    ?or:         expr   symb_or    expr      -> disj
-    ?or_long:  [ expr ( symb_or    expr )+ ] -> disj_lang
-    ?impl:       expr   symb_impl  expr      -> impl
-    ''',
-    regex=True
-);
+with open('aussagenlogik/grammar.lark', 'r') as fp:
+    grammar = ''.join(fp.readlines());
+    lexerAussagenlogik = Lark(grammar, start='expr', regex=True);
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # KLASSE: Syntaxbaum
@@ -87,14 +54,15 @@ class SyntaxBaum(object):
             signature = ' '.join(signature_parts);
             self.expr = signature.format(*self.children);
             if self.kind in [ 'konj', 'konj_lang', 'disj', 'disj_lang', 'impl' ]:
-                self.expr = '( {} )'.format(self.expr);
+                self.expr = ('(' if self.expr.startswith('(') else '( ') + self.expr;
+                self.expr += (')' if self.expr.endswith(')') else ' )');
         return;
 
     def __str__(self):
         return self.expr;
 
     def pretty(self):
-        return self.tree.pretty();
+        return self.tree.pretty(indent_str='- ');
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # METHODE: string -> Syntaxbaum