how many company were founded in the same year as petri ag ?
select attr_open count attr_open distinct var_uri attr_close as var_c attr_close where brack_open var_uri rdf_type dbo_Company sep_dot var_uri dbo_foundingYear var_year sep_dot dbr_Petri_AG dbo_foundingYear var_year sep_dot dbr_Petri_AG a dbo_Companybrack_close