diff --git a/assets/section_2.3_1686916498071_0.edn b/assets/section_2.3_1686916498071_0.edn
new file mode 100644
index 0000000..5d9ecfe
--- /dev/null
+++ b/assets/section_2.3_1686916498071_0.edn
@@ -0,0 +1 @@
+{:highlights [], :extra {:page 3}}
diff --git a/assets/section_2.3_1686916498071_0.pdf b/assets/section_2.3_1686916498071_0.pdf
new file mode 100644
index 0000000..42b6540
Binary files /dev/null and b/assets/section_2.3_1686916498071_0.pdf differ
diff --git a/pages/总复习2023t1.md b/pages/总复习2023t1.md
index b4971d2..8060766 100644
--- a/pages/总复习2023t1.md
+++ b/pages/总复习2023t1.md
@@ -2695,28 +2695,30 @@
 						- ((648c290a-3532-4e56-8536-258daf7b00a7))
 					- Distribution Function
 						- ((648c2970-9091-4f46-8745-b0c10cdeb832))
+						  collapsed:: true
 							- ((648c2994-36eb-44bf-8038-e49d2390a5b0))
 						- ((648c2a73-3961-4723-90e8-5f160bb18e0d)) ![section 2.2.pdf](../assets/section_2.2_1686907456219_0.pdf)
+						  collapsed:: true
 							- ((648c2a88-3d0f-47d2-be44-21df002a1def))
 							- ((648c2abf-5c5e-4af9-9e13-bb566f3206e8))
 							- ((648c2b26-e92d-43f7-b8e1-60b51a2b5268))
 						- Discrete type
+						  collapsed:: true
 							- Definition:  ((648c2be0-787e-4e1f-8d0c-b859f0d08383))
 						- Continuous type
+						  collapsed:: true
 							- ((648c2c54-b536-40ba-8191-ef1aeb2be0b9))
 					- ((648c2c9a-fcca-43e3-94a6-466f52131b48))
 						- ((648c2d05-82d4-472f-901c-b362852e2a3a))
 						- 换元的示例
+						  collapsed:: true
 							- ((648c2de1-d9a7-4760-bb4f-beec4b41102c))
 							- ((648c488f-85fa-4203-8092-07176b38fce9))
 						- 公式法 #flashcard
+						  collapsed:: true
 							- ((648c48ac-76be-4848-af0d-1532467c8d68))
-					- ((648c4c04-61cb-4d8a-ae01-257a5edd0430)) ![section 2.2.pdf](../assets/section_2.2_1686916081846_0.pdf)
-						- Properties
-							- ((648c4c7a-0eb7-4ba3-b538-5a8358cd98f5))
-							- ((648c4c85-d834-412f-b925-2727e7e1c2ac))
-							- ((648c4d11-8654-467e-996c-8df5eb48a598))
-							-
+					- Mathematical Expectation and Variance ![section 2.3.pdf](../assets/section_2.3_1686916498071_0.pdf)
+						- Expectation
 			- LATER 学积分
 			  :LOGBOOK:
 			  CLOCK: [2023-06-03 Sat 17:05:07]--[2023-06-03 Sat 17:05:08] =>  00:00:01