diff --git a/lecture03/math-research-assistant/services/knowledge_base/knowledge_base.py b/lecture03/math-research-assistant/services/knowledge_base/knowledge_base.py
index f6a4c67..0b4335a 100644
--- a/lecture03/math-research-assistant/services/knowledge_base/knowledge_base.py
+++ b/lecture03/math-research-assistant/services/knowledge_base/knowledge_base.py
@@ -2,9 +2,11 @@
 import random
 from abc import *
 from enum import Enum
+from services.knowledge_base.math_object import IMathObject
 
 
 class IKnowledgeBase(metaclass = ABCMeta):
 
     @abstractmethod
-    def find_obj(self, obj_name): pass
+    def find_obj(self, obj_name : str) -> IMathObject:
+        pass
diff --git a/lecture03/math-research-assistant/services/knowledge_base/math_object.py b/lecture03/math-research-assistant/services/knowledge_base/math_object.py
index f50fe3c..4fab340 100644
--- a/lecture03/math-research-assistant/services/knowledge_base/math_object.py
+++ b/lecture03/math-research-assistant/services/knowledge_base/math_object.py
@@ -7,17 +7,18 @@
 class IMathObject(INotion, metaclass = ABCMeta):
 
     @abstractmethod
-    def get_description(self): pass
+    def get_description(self) -> str:
+        pass
 
 
 
 class GenericMathObject(IMathObject):
-    def __init__(self, name, description):
+    def __init__(self, name : str, description : str):
         self.__name = name
         self.__description = description
 
-    def get_name(self):
+    def get_name(self) -> str:
         return self.__name
 
-    def get_description(self):
+    def get_description(self) -> str:
         return self.__description
diff --git a/lecture03/math-research-assistant/services/knowledge_base/notion.py b/lecture03/math-research-assistant/services/knowledge_base/notion.py
index 4ee8cc6..2b8c79f 100644
--- a/lecture03/math-research-assistant/services/knowledge_base/notion.py
+++ b/lecture03/math-research-assistant/services/knowledge_base/notion.py
@@ -6,4 +6,5 @@
 class INotion(metaclass = ABCMeta):
 
     @abstractmethod
-    def get_name(self): pass
+    def get_name(self) -> str:
+        pass