user: Question: When was the start of the construction of the unit that's been in commercial operation since 04.03.1987?
Columns: ['Unit', 'Type', 'Net power', 'Total power', 'Construction start', 'Construction finish', 'Commercial operation', 'Shut down']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Chinon A1', 'Magnox-Reactor', '70 MW', '80 MW', '01.02.1957', '14.06.1963', '01.02.1964', '16.04.1973']
SQL:

assistant: SELECT "Construction start" FROM "Table" WHERE "Commercial operation" = '04.03.1987';