Terminology and notation
Capital latin letters are used to denote sets of points and their Boolean analogue, elements of Boolean algebras. Capital gothic letters denote classes of sets and their Boolean analogue, sets of elements of Boolean algebras (except for filters and ideals). In particular, 𝔄 and 𝔅 (with indices, if necessary) always denote Boolean algebras or fields of sets. The letter 𝔉 always denotes a field of sets.