Catholic Encyclopedia article on "Ecumenical Councils:" https://www.newadvent.org/cathen/04423f.htm
This subject will be treated under the following heads:
The Pope and General Councils
Composition of General Councils
Right of participation
Requisite number of members
Papal headship the formal element of Councils
Factors in the Pope's Co-operation with the Council
Infallibility of General Councils;
Correlation of Papal and Conciliary Infallibility
Infallibility Restricted to Unanimous Findings
Is a Council above the Pope?
Has a General Council Power to Depose a Pope?