The "Catholic Encyclopedia" in 1913 said: "The pope himself, if notoriously guilty of heresy, would cease to be pope because he would cease to be a member of the Church." Likewise, theologians Wernz-Vidal, commentary on Canon Law:"Ius canonicum":Through notorious and openly divulged heresy, the Roman Pontiff, should he fall into heresy, by that very fact "(ipso facto)" is deemed to be deprived of the power of jurisdiction even before any declaratory judgment by the Church... A Pope who falls into public heresy would cease "ipso facto" to be a member of the Church; therefore, he would also cease to be head of the Church.There are estimated to be between several tens of thousands and more than two hundred thousand sedevacantists worldwide, mostly concentrated in the United States, Canada, France, the UK, Italy, and Australia, but the actual size of the sedevacantist movement has never been accurately assessed. It remains extremely difficult to establish the size of the movement for a wide range of reasons – not all sedevacantists identify themselves as such, nor do they necessarily adhere to sedevacantist groups or societies. (See further the section on statistics in the article "Traditionalist Catholic".) Catholic doctrine teaches the four marks of the true Church are that it is One, Holy, Catholic, and Apostolic. Sedevacantists base their claim to be the remnant Catholic Church on what they see as the presence in them of these four "marks", absent, they say, in the Church since the Second Vatican Council. Their critics counter that sedevacantists are not one, forming numerous splinter groups, each of them in disagreement with the rest. Most sedevacantists hold the Holy Orders conferred with the present revised rites of the Catholic Church to be invalid due to defect both of intention and form. Because they consider the 1968 revision of the rite of Holy Orders to have invalidated it, they conclude that the great majority of the bishops listed in the Holy See's "Annuario Pontificio", including Benedict XVI and Francis themselves, are in reality merely priests or even laymen.