4S B Hendricks Electron distribution in (NH4)2 C2 04 - H2 O and the structure of the oxalate Group [J]. J Chem phys 4(1936) 102.
5S A Pyane. LiCaA1F6:Cr3+.. A Promising nwe solid State laser material [J]. IEEE Quantumn Electrics, 1988,24(11) : 2243-2252 .
6Ram Kripal, Manisha Bajpai and A K Shukla. EPR and optical absorption study of Cr3+-doped ammonium ox-alate monohydrate single crystals[J]. Physica B, 404 (2009) :82-88.
7Y Y Yeung and C Rudowiez. Ligand field analysis of the 3dN ions at orthorhombic or higher symmetry sites [J]. 2omputers and chemistry, 16, 1992, 207-216.