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Publication and Citation Analysis

Small (1986, 1993). Subjectivity enters in the choice of clustering
algorithm and in the choice of a threshold value.
Similar to the case of bibliographic coupling we use the notation of
Subsection 5.9.3 and matrices to describe the cocitation strength of two
documents d i and d j with C the citation matrix of the field including d i
and d j . This value is given by:

m
X
t
c ki c kj 5 C CÞ (5.10)
ð
ij
k51
Terms in the sum on the left hand side are zero or one. The value one
only happens in the case that documents d i and d j are cited by document
d k . These occurrences are added, yielding the cocitation strength. Finally
t
t
C CÞ 5 P m C Þ : C 5 P m
c
ð ij k51 ð ik ðÞ kj k51 ki c kj .
Martyn’s (1964) criticism on bibliographic coupling also applies to
cocitation analysis. The fact that two papers are cocited does not imply
that they contain similar pieces of information. Probably David Edge was
the strongest opponent of cocitation analysis without human judgment.
In his two papers Why I am not a cocitationist (Edge, 1977) and Quantitative
measures of communication in science: a critical review (Edge, 1979) he
expresses the view that quantitative methods such as cocitation analysis
have only limited use. Among other objections he emphasizes the need to
be able to see individual variations. It is often because individual scientists
and groups do not share the consensus view, as shown by cocitation
maps, that crucial innovative decisions are made.
Next we propose an exercise on bibliographic coupling and
cocitation.
Consider articles A, B, C, and D. Their reference lists are shown in
Table 5.7. Determine the order in which these articles are written. Next,
determine the bibliographic coupling of each two articles and their rela-
tive bibliographic coupling. When this is done, determine the cocitation
frequency and relative cocitation of each pair of articles occurring in at
least one reference list. Article D does not belong to any reference list,
and hence is not considered for this part (one may say that its cocitation
frequency with any of the other articles is zero).
Solution
Among these articles article A was written first, followed, in this order,
by articles C, B, and D. Indeed, A is in the reference list of C (and hence