M  N  L                                   | <--- rows, columns, entries
% |    I1  J1  A(I1, J1)                         | <--+
% |    I2  J2  A(I2, J2)                         |    |
% |    I3  J3  A(I3, J3)                         |    |-- L lines
% |        . . .                                 |    |
% |    IL JL  A(IL, JL)                          | <--+
% +----------------------------------------------+
%
% Indices are 1-based, i.e. A(1,1) is the first element.
%
%=================================================================================
  5  5  8
    1     1   1.000e+00
    2     2   1.050e+01
    3     3   1.500e-02
    1     4   6.000e+00
    4     2   2.505e+02
    4     4  -2.800e+02
    4     5   3.332e+01
    5     5   1.200e+01
a