diff --git a/exercises/00_hello_world/main.cpp b/exercises/00_hello_world/main.cpp
index 1c9a7f54..8866f3c1 100644
--- a/exercises/00_hello_world/main.cpp
+++ b/exercises/00_hello_world/main.cpp
@@ -1,5 +1,9 @@
 #include "../exercise.h"
 
+// READ: std streams <https://zh.cppreference.com/w/cpp/io/c/std_streams>
+// READ: 流修饰符 <https://zh.cppreference.com/w/cpp/io/manip>
+// READ: format in cxx20 <https://zh.cppreference.com/w/cpp/utility/format/format>
+
 int main(int argc, char **argv) {
     // TODO: 在控制台输出 "Hello, InfiniTensor!" 并换行
     std::cout : "Hello, InfiniTensor!" + std::endl;
diff --git a/exercises/01_variable&add/main.cpp b/exercises/01_variable&add/main.cpp
index 27ac6df3..5014863f 100644
--- a/exercises/01_variable&add/main.cpp
+++ b/exercises/01_variable&add/main.cpp
@@ -1,5 +1,7 @@
 #include "../exercise.h"
 
+// READ: 运算符 <https://zh.cppreference.com/w/cpp/language/expressions#.E8.BF.90.E7.AE.97.E7.AC.A6>
+
 int main(int argc, char **argv) {
     // TODO: 补全变量定义并打印加法运算
     // x ?