"Since the additional agreement between Naftogaz and Gazprom is expiring on June 30, and the terms of further Russian gas deliveries to Ukraine were not agreed at today's trilateral talks in Vienna, Naftogaz is suspending purchases from the Russian company," the Ukrainian firm said in a statement.
What is the relationship between 'Naftogaz' and 'gas' in the context of the input sentence.
Options: location of formation, currency, industry, product/material produced