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.

But in cases of firms like Aircel, for instance, it can trade most of its liberalized 2300MHz spectrum with Vodafone or Idea – trading with Bharti Airtel could run up against the caps which prohibit a telco from owning more than 50% of the spectrum in any band or 25% across all bands.

Answer: owned_by: Bharti Airtel, Vodafone