не могу понять,почему не видит ссылки

#include <iostream>
#include "Payment.h"
#include <string>
#include <sstream>
 
 
using namespace std;
 
int main()
{
    payment worker1;
    payment worker2 ("ivan", "ivan", "ivan", 10000,2005,10,5);
    payment worker3(worker2);
    int stah = worker2.experience();
    cout << worker1 << endl;
    string s = worker2.toString();
    cout << s <<endl;
    cin >> worker1;
    cout << worker1 << endl;
    cout << worker2 << endl;
    cout << worker1 << endl;
    cout <<"Stah:"<< stah << endl;
    double money = worker2.accruals(), no_money = worker2.withholding ();
    cout << money<<"-"<<no_money <<endl;
    return 0;
}
 
 
 
Payment.h/////
 
 
#ifndef PAYMENT_H_INCLUDED
#define PAYMENT_H_INCLUDED
 
#include <string>
#include <iostream>
#include <sstream>
 
using namespace std;
 
class payment{
private:
    string surname, name, patronymic;
    double salary, year;
    int otr_day, rab_day;
    static const double salary_per_day, tax, percent;
public:
    payment ();
    payment (string, string, string, double, double, int, int);
    payment (const payment&);
    string toString() const;
    int experience ();
    double accruals ();
    double withholding ();
    friend ostream& operator << (ostream&, const payment&);
    friend istream& operator >> (istream&, payment&);
    };
 
#endif // PAYMENT_H_INCLUDED
 
 
 
Payment.cpp///
 
 
#include <iostream>
#include "Payment.h"
#include <string>
#include <sstream>
 
using namespace std;
 
const double payment::salary_per_day = 100;
const double payment::tax = 0.13;
const double payment::percent = 0.1;
 
payment :: payment(): surname("Surname"), name("Name"), patronymic("Patronymic"), salary(0.0), year(0.0), otr_day(0), rab_day(0){};
payment :: payment (string _surname, string _name, string _patronymic, double _salary,double _year, int _otr_day, int _rab_day):
    surname(_surname),name(_name),patronymic(_patronymic),
    salary(_salary),year(_year),
    otr_day(_otr_day),rab_day(_rab_day){};
payment :: payment (const payment &other) {
    surname = other.surname;
    name = other.name;
    patronymic = other.patronymic;
    salary = other.salary;
    year = other.year;
    otr_day = other.otr_day;
    rab_day = other.rab_day;
}
std::string payment :: toString () const {
    std::ostringstream oss;
    oss << surname <<" " <<name<<" "<< patronymic << ",salary = " << salary << ",year = " << year <<","<< otr_day <<","<< rab_day;
    return oss.str();
}
 
int payment :: experience() {
    return int (2018 - year);
}
double payment :: accruals () {
    return double ((1 + percent) * salary_per_day * otr_day );
}
double payment::withholding() {
    return double ((1 + percent) * salary_per_day * otr_day * tax + (1 + percent) * salary_per_day * otr_day * 0.1);
}
ostream& operator << (ostream& out, const payment&p) {
    out << p.surname <<" "<< p.name<<" "<< p.patronymic << "," <<p.salary << "," << p.year <<","<< p.otr_day <<","<< p.rab_day;
    return out;
}
istream& operator >> (istream&in, payment&p) {
    in >>  p.surname >> p.name>> p.patronymic >>p.salary >> p.year>>p.otr_day >> p.rab_day;
    return in;
}