Berdayev, Nikolai Alexandrovich (1874-1948) -- a reactionary idealist philosopher and publicist.
The reference here is to his article "The Fight for Idealism", published in the journal Mir Bozhy No. 6, for 1901.
Struvefreundliche Partei -- the name by which Potresov and Zasulich were jokingly called among the editorial staff of Iskra.
The reference is to the books: N. Shakhovskoi, Agricultural Outside Employments, Moscow, 1896; N. I. Tezyakov, Agricultural Workers and the Organisation of Sanitary Supervision Over Them in Kherson Gubernia, Khersoll, 1896.
The preface to Witte's "memorandum" was written by P. B. Struve. Lenin "trounced" Struve's preface in Chapter V of his article "The Persecutors of the Zemstvo and the Hannibals of Liberalism" (see Vol. 5 of this edition).
This refers to Nevzorov's (Y. M. Steklov's) article "And So, Where Do We Begin?" directed against Lenin's article "Where To Begin" (see Vol. 5 of this edition).