• Afterwards, SBUs are formed by regrouping together all adjacent atoms belonging to the same class. Paddle-wheel patterns are identified separately and regrouped into a single inorganic SBU even when the two opposite metal centres are not bonded together. The points of extension, which are organic atoms bonded to an inorganic atom, form their own SBU each. The algorithm stops here if there is no periodic SBU, i.e. if there is no infinite set of adjacent atoms belonging to the same class.