CREATE TABLE table_26990 ("Expedition" TEXT, "Crew" TEXT, "Launch date" TEXT, "Flight up" TEXT, "Landing date" TEXT, "Flight down" TEXT, "Duration  ( days ) " TEXT)

Name the duration for vladimir vasyutin , alexander volkov
SELECT COUNT("Duration (days)") FROM table_26990 WHERE "Crew" = 'Vladimir Vasyutin , Alexander Volkov'
SELECT COUNT("Duration (days)") FROM "table_26990" WHERE "Crew" = 'Vladimir Vasyutin , Alexander Volkov'