A data node (the child node) can be based on a data node (parent node). This means that the result table of the parent node is the input table for the first operation of the child node.
The figure on the right shows data node "z_01" based on its parent node "z_00 Input"
Hence, one or more data nodes (the referenced nodes) can be referenced by an operation in another data node. This creates dependencies between the data node and the referenced nodes.
The figure on the right shows a list of referenced data nodes (References) as tooltip in a List of Data Nodes.