Editorial introduction to the special issue on computational linear algebra and sparse matrix computations

Compounds of the formula wherein R1 represents C1 to C20 alkyl-substituted benzyl, or C2 to C20 alkyl which can optionally bear one or two -OR2 radicals, wherein each R2 independently represents hydrogen or the radical wherein R3 represents C1 to C20 alkyl are disclosed. These compounds are useful for the selective extraction of cobalt, nickel or copper ions from aqueous acidic ore leach liquors.