For Euro-PCT applications where the EPO acted as International Searching Authority (ISA) or as the authority specified for supplementary international search (SISA), any amendments which the applicant files in response to the communication under Rule 161(1) (see E‑IX, 3.3.4) are made by the applicant of his own volition. This means that they may be submitted to overcome objections raised in the WO-ISA, IPER or supplementary international search report or they may be suggested for some other reason, e.g. to remedy some lack of clarity which the applicant himself has noted in the original documents. In order to avoid delays, care should be taken to comply with the requirements of Rule 137(4) when filing such amendments. Furthermore, the applicant may also file observations in place of or in addition to amendments.