The determination of the origin of natural bitumen in mummifying resins of Ancient Egyptian mummies from the collection of the Pushkin Museum of Fine Arts oleh E. B. Yatsishina, V. M. Pozhidaev, O. A. Vasilyeva, O. P. Dyuzheva, Ya. E. Sergeeva, V. M. Retivov, E. Yu. Tereschenko, I. S. Kulikova, E. S. Vaschenkova, E. I. Kozhukhova