diff --git a/converter.py b/converter.py
index 9d63456..258d52e 100644
--- a/converter.py
+++ b/converter.py
@@ -12,7 +12,7 @@ class System:
     def __init__(
         self,
         name: str,
-        base: set[str],
+        base: list[str],
         axiom: str,
         substitutions: list[tuple[str, str]],
         interpretations: list[tuple[str, str]],
@@ -83,7 +83,7 @@ def data_reader(path: str, delimiter: str = ","):
         data = csv_reader(csv_file, delimiter=delimiter)
         for system in data:
             name = system[0]
-            base = set(system[1])
+            base = list(system[1])
             axiom = system[2]
             substitutions = [(v, system[3 + i]) for i, v in enumerate(base)]
             interpretations = [
@@ -91,6 +91,7 @@ def data_reader(path: str, delimiter: str = ","):
             ]
 
             res.append(System(name, base, axiom, substitutions, interpretations))
+
     return res