两个不同头文件中不同的类互相引用时出现连接问题

写了两个类在不同的头文件中

 #ifndef CUSTOMER_H_
#define CUSTOMER_H_
class Customer
{
private:
    double totle;
public:
    Customer();
    Customer(double mt);
    void save(double cush);
    int deposit(double cush);
    double get_tol();
};
typedef Customer Item;
#endif

 #ifndef QUENE_H_
#define QUENE_H_

class Quene
{
private:
    struct Node{Item item;Node *next;};
    enum{Q_Size=50};
    Node *front;
    Node *rear;
    int items;
    const int qsize;
public:
    //Quene();
    Quene(int size=Q_Size);
    ~Quene();
    bool isfull();
    bool isempty();
    int quenecount();
    bool enquene(const Item &item);
    bool dequene(Item& item);
};
#endif

报出如下错误：Error 1 error LNK1561: entry point must be defined C:\Users\asus\Desktop\quene\quene\LINK

1. Queue中引用了Customer，　为啥就成了互相引用了