International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 9.2, p. 767

Figure 9.2.2.7 

S. Ďuroviča
[Figure 9.2.2.7]
Figure 9.2.2.7

Two possible combinations of one tetrahedral and one octahedral sheet (a) by shared apical O atoms, (b) by hydrogen bonds (side projection).