a) Use of workers posted to the contractor by another company owned by the same group  and established in a Member State (“intra-group posting” as defined by Article 1, 3,  (b) of Directive 96/71/EC concerning the posting of workers in the framework of the  provision of services).  b) Use of workers hired out to the contractor by a temporary employment undertaking or  placement agency established in a Member State (“hiring out of workers” as defined  by Article 1, 3, (c) of Directive 96/71/EC concerning the posting of workers in the  framework of the provision of services).  c) Use of workers temporarily transferred to the contractor from an undertaking  established outside the territory of a Member State and that belongs to the same group  (“intra-corporate transfer” as defined by Article 3, (b) of Directive 2014/66/EU on the  conditions of entry and residence of third-country nationals in the framework of an  intra-corporate transfer) .  d) Use of staff without employment contract (“self-employed persons working for the  contractor”) to perform substantially the same tasks as the staff with employment  contract (“employees”), without the tasks of the self-employed persons being  particular well-defined parts of the contract.  e) Use of suppliers and/or transporters by the contractor, in order to perform the contract  at the place of performance, unless the economic activities of the suppliers and/or the  transporting services are within the subject of this call for tender (see  Section 1.4 ). f) Performance of part of the contract by members of an EEIG (European Economic  Interest Grouping), when the EEIG is itself a contractor or a group member.  The persons mentioned in points a), b), c) and d) above will be considered as “personnel” of  the contractor as defined in the contract.  All contractual tasks may be subcontracted unless the  Technical specifications expressly  reserve the execution of certain critical tasks to the sole tenderer itself, or in case of a joint  tender, to a member of the group.  By filling in the form available in  Annex 4 , tenderers are required to give an indication of the  proportion of the contract that they intend to subcontract, as well as to identify and describe  briefly the envisaged contractual roles/tasks of subcontractors meeting any of these conditions  (hereafter referred to as  identified subcontractors ): Any such subcontractor must provide the tenderer with a commitment letter drawn up in the  model attached in  Annex 5.1  and signed by its authorised representative. Changes concerning subcontractors identified in the tender (withdrawal/replacement of a  subcontractor, additional subcontracting) during the procurement procedure (after the  submission deadline and before contract signature) require the prior written approval of the  Contracting authority  subject to the following verifications:   whose individual share of the contract, known at the time of submission, is above 20%  on whose capacities the tenderer relies upon to fulfil the selection criteria as described  under  Section 3.2 ;  any new subcontractor is not in an exclusion situation;  20