Columbia subject headings:
P. I︠A︡. (Petr I︠A︡kubovich), 1860-1911.
Harvard subject headings:
I︠A︡kubovich, Petr Fillipovich, 1860-1911.
Princeton subject headings:
P. I︠A︡. (Petr I︠A︡kubovich), 1860-1911.