  Van Raan et al. (2010; arXiv:1003.2113) have proposed a new indicator (MNCS)
for field normalization. Since field normalization is also used in the Leiden
Rankings of universities, we elaborate our critique of journal normalization in
Opthof & Leydesdorff (2010; arXiv:1002.2769) in this rejoinder concerning field
normalization. Fractional citation counting thoroughly solves the issue of
normalization for differences in citation behavior among fields. This indicator
can also be used to obtain a normalized impact factor.
