  In complex networks the rich nodes are the subset of nodes with high degree.
These well connected nodes tend to dominate the organisation of the network's
structure. In non-evolving networks, a reference network has been used to
detect if the connectivity between the rich nodes is due to chance or caused by
an unknown mechanism. Chance is represented as a reference network obtained
from an ensemble of networks. When compared with the original network the
reference network discounts suggests the existence of a well connected rich
club beyond structural constraints. Here we revise some of the properties of
the ensemble obtained by conserving only the degree distribution and introduce
two new reference networks to study the importance of the rich nodes as
organisers of the network structure. The first reference network is obtained
from an ensemble of networks where all the members of the ensemble have the
same rich--club coefficient. The reference network obtained from the ensemble
is assortative. We propose that this reference network can be used to study
networks where assortativness is a fundamental property, a common case in many
social networks. The second reference network is obtained from an ensemble
where the members of the ensemble all have the same probability degree
distribution and rich-club coefficient. The reference network obtained from
this ensemble has a very similar structure to the original network. This
ensemble can be used to quantify correlations between the rich nodes and
pinpoint which links are the backbone of the network's structure.
