Simplify the following text for a Grade 15 native English-speaking person.
Original: At the December 1969 IRA convention and the January 1970 Sinn FÃ in Ard Fheis ( the Irish words for a party conference or convetion ) the delegates voted to participate in the Dublin ( Leinster House ) , Belfast ( Stormont ) and London ( Westminster ) parliaments , the organizations split into Provisional and Official parts .
Simplified: When , at the December 1969 IRA convention and the January 1970 Sinn FÃ in Ard Fheis the delegates voted to participate in the Dublin ( Leinster House ) , Belfast ( Stormont ) and London ( Westminster ) parliaments , the organizations split .