This library is meant for the calculation of matrix elements of any one- or two- particle operator. It contains 44 subroutines. Most of the subroutines from this module use common blocks CONSTS and MEDEFN from MCHF atomic structure package [1,11]. Similar to the SAI_NORE library, it uses the methodology described in paper P2 [4]. Therefore the arrangement of library SAI_DUDU is analogous to that of library SAI_NORE. Therefore we will not go into computational details of angular parts of one- or two- particle operator matrix elements, but instead will reserve all the attention to a demonstration connecting the Breit-Pauli operators to the general algorithm of one- or two- particle operator calculation.