id	keyword
american_scientific_journal-3297	refrigerants
american_scientific_journal-3297	r134a
american_scientific_journal-3297	r12
american_scientific_journal-3297	alternative
american_scientific_journal-3297	r1234yf
american_scientific_journal-3297	r600a
american_scientific_journal-3297	refrigerator
american_scientific_journal-3297	journal
american_scientific_journal-3297	r290
american_scientific_journal-3297	heat