Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_26990 ( "Expedition" text, "Crew" text, "Launch date" text, "Flight up" text, "Landing date" text, "Flight down" text, "Duration (days)" text )

### Question ###
Name the duration for vladimir vasyutin , alexander volkov

### Accurate SQL ###

SELECT COUNT("Duration (days)") FROM table_26990 WHERE "Crew" = 'Vladimir Vasyutin , Alexander Volkov'