Add punctuation: Overall amniocentesis is a safe procedure with the risk of fetal loss at generally less than 1 According to the American College of Obstetricians and Gynecologists Practice Bulletin there is a procedurerelated rate of fetal loss ranging from 1300 to 1500 procedures
A: Overall, amniocentesis is a safe procedure with the risk of fetal loss at generally less than 1%. According to the American College of Obstetricians and Gynecologists Practice Bulletin, there is a procedure-related rate of fetal loss ranging from 1/300 to 1/500 procedures.

Add punctuation: The revised treaty provided for the withdrawal of British troops over a twenty month period
A: The revised treaty provided for the withdrawal of British troops over a twenty month period.

Add punctuation: When spring approaches the evenings begin to get lighter and it is usually then that most people become tired of lectures
A:
When spring approaches, the evenings begin to get lighter and it is usually then that most people become tired of lectures.