ORACLE PL/SQL oracle column ambiguously defined

SELECT first_name,last_name,start_date,salary,job_title,
                          department_name,street_address,postal_code,city,
                          country_name,region_name
                FROM 
                HR.EMPLOYEES INNER JOIN  HR.JOB_HISTORY ON HR.EMPLOYEES.employee_id=HR.JOB_HISTORY.employee_id ,
                HR.JOBS INNER JOIN HR.EMPLOYEES ON HR.JOBS.job_id=HR.EMPLOYEES.job_id,
                HR.DEPARTMENTS INNER JOIN HR.EMPLOYEES ON HR.DEPARTMENTS.department_id=HR.EMPLOYEES.department_id,
                HR.LOCATIONS INNER JOIN HR.DEPARTMENTS ON HR.LOCATIONS.location_id=HR.DEPARTMENTS.location_id,
                HR.COUNTRIES INNER JOIN HR.LOCATIONS ON HR.COUNTRIES.country_id=HR.LOCATIONS.country_id,
                HR.REGIONS INNER JOIN HR.COUNTRIES ON HR.REGIONS.region_id=HR.COUNTRIES.region_id ;