CREATE TABLE table_12983929_1 (construction_start VARCHAR, commercial_operation VARCHAR)

When was the start of the construction of the unit that's been in commercial operation since 04.03.1987?
SELECT construction_start FROM table_12983929_1 WHERE commercial_operation = "04.03.1987"
SELECT "construction_start" FROM "table_12983929_1" WHERE "04.03.1987" = "commercial_operation"