High-pressure synthesis of borate-nitrates: crystal structure of <i>M</i> <sub>3</sub>B<sub>7</sub>O<sub>13</sub>(NO<sub>3</sub>) (<i>M</i> = Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>)
Zeitschrift für Naturforschung. B, A journal of chemical sciences