Laws of Cricket 1980 Code - Law 13
1. Lead on First Innings
In a two-innings match the side which bats first and leads by 200 runs in a match of five days or more, by 150 runs in a three-day or four-day match, by 100 runs in a two-day match, or by 75 runs in a one-day match, shall have the option of requiring the other side to follow their innings.
2. Day's Play Lost
If no play takes place on the first day of a match of two or more days' duration, 1. above shall apply in accordance with the number of days' play remaining from the actualstart of the match.
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