When was Stellbrookmoor established?
CREATE TABLE table_28237 (
    "NSG Nr." real,
    "Name of the nature reserve" text,
    "District / Town" text,
    "Area (ha)" text,
    "Date established" text
)
SELECT "Date established" FROM table_28237 WHERE "Name of the nature reserve" = 'Stellbrookmoor'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: When was Stellbrookmoor established? ### Input: CREATE TABLE table_28237 (
    "NSG Nr." real,
    "Name of the nature reserve" text,
    "District / Town" text,
    "Area (ha)" text,
    "Date established" text
) ### Response: SELECT "Date established" FROM table_28237 WHERE "Name of the nature reserve" = 'Stellbrookmoor'