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.

Despite serving as a punching bag for media executives frustrated by mobile video, Nielsen is unlikely to be knocked from its perch as the industry standard for buying and selling advertising even as leading rivals  Rentrak ( RENT - Get Report ) and comScore ( SCOR - Get Report )  plan to merge.

Answer: owner_of: comScore, Rentrak