Given the input sentence, please extract the subject and object containing a certain relation in the sentence according to the following relation types, in the format of "relation1: word1, word2; relation2: word3, word4". Relations include: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Sept 18 Apple Inc is stepping up aid to the thousands of migrants that are streaming into Europe from war-torn countries, Chief Executive Officer Tim Cook told employees in an internal message on Friday.

Answer: chief_executive_officer: Apple Inc, Tim Cook; employer: Tim Cook, Apple Inc; position_held: Tim Cook, Chief Executive Officer