def bic_subjects
      subjects = product.subjects.select { |sub| sub.subject_scheme_id.to_i == 12 }
      subjects.collect { |sub| sub.subject_code}
    end
def bic_subjects
      subjects = product.subjects.select { |sub| sub.subject_scheme_id.to_i == 12 }
      subjects.collect { |sub| sub.subject_code}
    end
return an array of BIC subjects for this title
 could be version 1 or version 2, most ONIX files don't
 specifiy