In model

                  
                   class department(osv.osv):
        _name = 'department'

        _columns = {
                 'name': fields.char('Department', size=32, required=True),
        }

    class djelatnik(osv.osv):
        _name = 'employee'

        _columns = {
            'name': fields.char('name',size=30, required=True, help='name'),
            'surname': fields.char('surname', size=30, required=True, help='surname'),
            'odjel': fields.many2one('department' ,'Departments')           
        }  
            

in view

            <record model="ir.ui.view" id="view_employee_form">
            <field name="name">employee.form</field>
            <field name="model">employee</field>
            <field name="type">form</field>
            <field name="arch" type="xml">
                <form string="employee">                   
                    <field name="name" select="1"/>
                    <field name="surname" select="2"/>
                    <field name="odjel" select='0'/>
                </form>
            </field>
        </record>
        <record model="ir.ui.view" id="view_employee_tree">
            <field name="name">employee.tree</field>
            <field name="model">employee</field>
            <field name="type">tree</field>
            <field name="arch" type="xml">
                <tree string="employee">
                    <field name="name"/>
                    <field name="surname"/>
                     <field name="odjel"/>
                </tree>
            </field>
        </record>
        <record model="ir.actions.act_window" id="action_employee">
            <field name="name">employee</field>
            <field name="res_model">employee</field>
            <field name="view_type">form</field>
            <field name="view_mode">tree,form</field>
            <field name="context">{"search_default_type_date":0}</field>
        </record>
        <menuitem name="HR/HR" id="menu_employee" action="action_employee"/>
        <menuitem name="employee" id="menu_employee_employee_item" parent="menu_employee" action="action_employee"/>

        <record model="ir.ui.view" id="view_department_form">
            <field name="name">department.form</field>
            <field name="model">department</field>
            <field name="type">form</field>
            <field name="arch" type="xml">
                <form string="department">                   
                    <field name="name" select="1"/>
                </form>
            </field>
        </record>
        <record model="ir.ui.view" id="view_department_tree">
            <field name="name">department.tree</field>
            <field name="model">department</field>
            <field name="type">tree</field>
            <field name="arch" type="xml">
                <tree string="odjel">
                    <field name="name"/>
                </tree>
            </field>
        </record>
        <record model="ir.actions.act_window" id="action_department">
            <field name="name">department</field>
            <field name="res_model">department</field>
            <field name="view_type">form</field>
            <field name="view_mode">tree,form</field>
        </record>
        <menuitem name="department" id="menu_department_department_item" parent="menu_employee" action="action_department"/>