  The weak variant of Hanani-Tutte theorem says that a graph is planar, if it
can be drawn in the plane so that every pair of edges cross an even number of
times. Moreover, we can turn such a drawing into an embedding without changing
the order in which edges leave the vertices. We prove a generalization of the
weak Hanani-Tutte theorem that also easily implies the monotone variant of the
weak Hanani-Tutte theorem by Pach and T\'oth. Thus, our result can be thought
of as a common generalization of these two neat results. In other words, we
prove the weak Hanani-Tutte theorem for strip clustered graphs, whose clusters
are linearly ordered vertical strips in the plane and edges join only vertices
in the same cluster or in neighboring clusters with respect to this order. In
order to prove our main result we first obtain a forbidden substructure
characterization of embedded strip clustered planar graphs.
  The Hanani-Tutte theorem says that a graph is planar, if it can be drawn in
the plane so that every pair of edges not sharing a vertex cross an even number
of times. We prove the variant of Hanani-Tutte theorem for strip clustered
graphs if the underlying abstract graph is three connected or a tree. In the
case of trees our result implies that c-planarity for flat clustered graphs
with three clusters is solvable in a polynomial time if the underlying abstract
graph is a tree. The proof of the latter result combines our forbidden
substructure characterization of embedded strip clustered planar graphs with
Tucker's characterization of 0-1 matrices with consecutive ones property.
