The rules that use the category "<id_letter-pl>" are:

<bare_company_id>

<company_noun-pl> <id_letter-pl>

<id_letter-pl> <company_noun-pl>

<company_id-not_creatable>

<company_type-pl> <id_letter-pl>

<id_letter-pl> <company_noun-pl>

<company_id-not_creatable-pl>

<company_type-pl> <id_letter-pl>

<id_letter-pl> <company_noun-pl>