Some bibliometric methods for the assessment of the publication activity of research units are discussed on the basis of impact factors and citations of papers. Average subfield impact factor of periodicals representing subfields in chemistry is suggested. This indicator characterizes the average citedness of a paper in a given subfield. Comparing the total sum of impact factors of corresponding periodicals divided by the number of papers published by a research team to the average subfield impact factor a publication strategy indicator can be derived. A new bibliometric indicator, relative subfield impact, is introduced which compares the number of citations received by papers of a research unit to the average subfield impact factor.