tokens: Several DNA clones were obtained by this procedure , one of which , clone 18 , is reported and characterized here .
folded_tokens: several dna clones were obtained by this procedure , one of which , clone 18 , is reported and characterized here .
labels: O B-DNA_molecule I-DNA_molecule O O O O O O O O O O B-DNA_molecule I-DNA_molecule O O O O O O O