What class members require initializer list in definition of constructor

Member objects of classes without default constructors
Const members
Reference members

Assume that T2 in the following does not have default constructor
Class MyClass
{
       string name;
       const int i;
       T1&  obj1;
       T2 obj2;
       MyClass(){};           //wrong - i, T1, T2 require initialization in the initializer list
}

Adding  following constructor(and corresponding declaration in the class declaration) would fix the issue
MyClass::MyClass(const int _i, T1& _obj1, T2 _obj2):_i(i), obj1(_obj1), obj2(_obj2){}

Ref. C++ Language, The (3rd Edition) by Bjarne Stroustrup , page 248.