  Scientific journals are the repositories of the gradually accumulating
knowledge of mankind about the world surrounding us. Just as our knowledge is
organised into classes ranging from major disciplines, subjects and fields to
increasingly specific topics, journals can also be categorised into groups
using various metrics. In addition to the set of topics characteristic for a
journal, they can also be ranked regarding their relevance from the point of
overall influence. One widespread measure is impact factor, but in the present
paper we intend to reconstruct a much more detailed description by studying the
hierarchical relations between the journals based on citation data. We use a
measure related to the notion of m-reaching centrality and find a network which
shows the level of influence of a journal from the point of the direction and
efficiency with which information spreads through the network. We can also
obtain an alternative network using a suitably modified nested hierarchy
extraction method applied to the same data. The results are weakly
methodology-dependent and reveal non-trivial relations among journals. The two
alternative hierarchies show large similarity with some striking differences,
providing together a complex picture of the intricate relations between
scientific journals.
