In its judgment of April 5, 2006 (- 4 AZR 390/05 -), the Fourth Senate decided that an employment contractual clause that refers to a collective regulation with regard to classification and remuneration does not necessarily cover regulations on working hours. Working hours and remuneration have a synallagmatic connection. However, this does not preclude a reference clause in an employment contract that refers to several collective regulations from being interpreted as meaning that the working hours to be performed by the employee are based on one collective regulation and the remuneration owed by the employer for this is based on another collective regulation. If the scope of weekly working hours is determined according to the employment contract or a referenced collective set of rules, the employee – if reference is made to another collective set of rules with regard to classification and remuneration – is entitled to the remuneration that an employee receives within the scope of the reference the collective set of rules adopted can demand the same grouping for the actual working hours to be performed. In the decision, the Fourth Senate was able to leave open whether a dynamic reference clause to a specific regulatory area of a third-party collective agreement when it is amended by a complex restructuring collective agreement leads to the referenced regulatory area in the amended version of the restructuring collective agreement being applied in isolation to the employment relationship. An argument against this could be that restructuring collective agreements are special regulations that respond to an atypical, particularly economically difficult situation in the immediate area of application of the collective agreement.