  In topological semimetals and nodal superconductors, band crossings between
occupied and unoccupied bands form stable nodal points/lines/surfaces carrying
quantized topological charges. In particular, in centrosymmetric systems, some
nodal structures at the Fermi energy $E_F$ carry two distinct topological
charges, and thus they are called doubly charged nodes. Here we show that
doubly charged nodal surfaces of centrosymmetric superconductors in
three-dimensions always develop peculiar linking structures with nodal points
or lines formed between occupied bands below $E_F$. Such linking structures can
naturally explain the inherent relationship between the charge of the node
below $E_F$ and the two charges of the nodal surfaces at $E_F$. Based on the
Altland-Zirnbauer (AZ)-type ten-fold classification of nodes with additional
inversion $\mathcal{I}$ symmetry, which is called the AZ$+\mathcal{I}$
classification, we provide the complete list of linking structures of doubly
charged nodes in centrosymmetric systems. The linking structures of doubly
charged nodes clearly demonstrate that not only the local band structure around
the node but also the global band structure play a critical role in
characterizing gapless topological phases.
