CREATE TABLE table_26986 ("Expedition" TEXT, "Crew" TEXT, "Launch date" TEXT, "Flight up" TEXT, "Landing date" TEXT, "Flight down" TEXT, "Duration  ( days ) " TEXT)

Name the duration for georgi grechko
SELECT "Duration (days)" FROM table_26986 WHERE "Crew" = 'Georgi Grechko'
SELECT "Duration (days)" FROM "table_26986" WHERE "Crew" = 'Georgi Grechko'