The hired copyist ("sestra")

An unnamed woman Chekhov has hired to copy out Sakhalin research materials, taking over the Rumyantsev Library visits from his brother Alexander starting the third week of Lent 1890. The Russian "сестра" ("sister") here is a period colloquial term for a hired female assistant/lay helper, not a kinship term -- this figure is NOT Chekhov's actual sister Maria Pavlovna Chekhova, who is not mentioned in this letter. Flagged explicitly to prevent conflation between the two.