I cordially thank you for sending me No 2 of your Social-Democrat  and am endeavouring to show you by the superscription of this letter that I am at least beginning to understand your language. The requirements of internationalism are growing with each year. Up to 1848 one believed one had done enough if one had a smattering of the main languages of Western and Central Europe, but now a point has been reached where I must in my old age learn even Rumanian and Bulgarian if I want to follow the progress of socialism eastward and south-eastward. However for all that we in the West rejoice no less over these our south-eastern vanguards on the Asian frontier, who are carrying as far as the Black Sea and the Aegean Sea the banner of the modern proletariat that Marx has unfurled if only he had lived to see this! and who answer the enticements and threats of Russian Tsarism by countering the tsarist proclamations with socialist works written by the Russian champions of the proletariat. It has given me great pleasure to see Plekhanov s works translated into Bulgarian. Long Live International Socialism!
Letters: Karl Marx and Frederick Engels, Selected Correspondence 1893