A precise quotation from Alma Mahler's memoirs needed

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In the 'The Mahler Companion' edited by Donald Mitchell  and Andrew Nicholson Inna A. Barsova wrote on p. 518:

In  Dostoyevsky Mahler found his own ethical outlook formulated: 'How can one be happy while a single being on earth still suffers', Alma reports him often saying, (7)...

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7) Alma Mahler, Memoirs, 20

Could anybody here be so kind as to provide me with the exact Alma's words (along with neighboring sentences)

Thank you

Boris