Recovering Zipf's law in intercontinental scientific collaboration

Scientific cooperation on an international level has been well studied in the literature. However, much less is known about this cooperation on the intercontinental level. In this paper, we address this issue by creating a collection of approximately 13.8 million publications around the papers by one of the highly cited author working in complex networks and their applications. The obtained rank-frequency distribution of the probability of sequences describing continents and number of countries -- with which authors of papers are affiliated -- follows the power law with an exponent $-1.9108(15)$. Such a dependence is known in the literature as Zipf's law and it has been originally observed in linguistics, later it turned out that it is very commonly observed in various fields. The number of distinct ``continent (number of countries)'' sequences in a function of the number of analyzed papers grows according to power law with exponent $0.527(14)$, i.e. it follows Heap's law.