International
Tables for Crystallography Volume A Spacegroup symmetry Edited by Th. Hahn © International Union of Crystallography 2006 
International Tables for Crystallography (2006). Vol. A. ch. 9.3, p. 757

Conventional cells are dealt with in Chapter 9.1 . They are illustrated in Fig. 9.1.7.1 and described in Table 9.1.7.2 . This description, however, is not exhaustive enough for determining the Bravais type. In mathematical terms, the conditions in Table 9.1.7.2 are necessary but not sufficient. For example, the Ccentred cell with has the typical shape of a conventional cell of an mC lattice. But the lattice generated by the Ccentred cell (9.3.4.1) is actually hR with the conventional rhombohedral basis vectors
It is a natural goal to establish a system of conditions for the conventional cells which would be not only necessary but also sufficient. This is done in Table 9.3.4.1. In order to make the conditions as simple as possible, the usual mC description of the monoclinic centred lattices is replaced by the mI description. The relation between the two descriptions is simple: The exact meaning of Table 9.3.4.1 is as follows: Suppose that a Bravais type different from aP is given and that its symbol appears in column 1 in the ith entry of Table 9.3.4.1. Then a lattice L is of this Bravais type if and only if there exists a cell (a, b, c) in L such that
