Is is shown, using rigorous statistical tests, that the number of journals (J) carryingp papers in a given subject can be expressed as a simple power law functionJ(p)=K p−γ, K and γ being constants. The standard maximum likelihood method of estimating γ has been suitably modified to take acoount of the fact thatp is a discrete integer variable. The parameter γ entirely characterises the scatter of articles in journals in a given bibliography. According to a dynamic model proposed earlier by the author, γ is a measure of the relative growth rates of papers and journals pertaining to the subject.