452 - 453 . the presidents of the OPA were : 




 1874 | 1875 | 1876 | 1877 | 1878 | 1879 | 
 1880 | 1881 | 1882 |
Head entity: 1878 Q7776 20
Tail entity: 1879 Q7783 22
Relation (head \u2192 tail): P156
Inverse relation (tail \u2192 head): P155