Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_26013618_1 (nsg_nr INTEGER, date_established VARCHAR)
### Question:
What Nature reserve number was established on 19961220 20.12.1996
### Answer:
SELECT MIN(nsg_nr) FROM table_26013618_1 WHERE date_established = "19961220 20.12.1996"