What is the relationship between Premier Oil and LONDON in the context of the input sentence. Choose an answer from: 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.

LONDON (ShareCast) - Premier Oil (LSE: PMO.L - news ) rallied after Jefferies upgraded the stock to 'buy' from 'hold' and raised the price target to 185p from 170p, on the basis of "continued operational delivery in 2H15".

Answer: headquarters_location