This paper focuses on the coauthor effect in different types of publications, usually not equally respected in measuring research impact. {\it A priori} unexpected relationships are found between the total coauthor core value, $m_a$, of a leading investigator (LI), and the related values for their publications in either peer review journals ($j$) or in proceedings ($p$). A surprisingly linear relationship is found: $ m_a^{(j)} + 0.4\;m_a^{(p)} = m_a^{(jp)} $. Furthermore, another relationship is found concerning the measure of the total number of citations, $A_a$, i.e. the surface of the citation size-rank histogram up to $m_a$. Another linear relationship exists : $A_a^{(j)} + 1.36\; A_a^{(p)} = A_a^{(jp)} $. These empirical findings coefficients (0.4 and 1.36) are supported by considerations based on an empirical power law found between the number of joint publications of an author and the rank of a coauthor. Moreover, a simple power law relationship is found between $m_a$ and the number ($r_M$) of coauthors of a LI: $m_a\simeq r_M^��$; the power law exponent $��$ depends on the type ($j$ or $p$) of publications. These simple relations, at this time limited to publications in physics, imply that coauthors are a "more positive measure" of a principal investigator role, in both types of scientific outputs, than the Hirsch index could indicate. Therefore, to scorn upon co-authors in publications, in particular in proceedings, is incorrect. On the contrary, the findings suggest an immediate test of coherence of scientific authorship in scientific policy processes.

22 pages; 2 Tables; 6 Figures; 38 references; prepared for Physica A