Original sentence: In recent years, some of these have been very controversial and high-profile, such as legalizing commercial gambling in 1993, Missouri Constitutional Amendment 2 (2006) (allowing the production of human embryos for stem cell research), Missouri Constitutional Amendment 2 (2004) (a  defense of marriage amendment prohibiting same-sex marriage), and an english-only amendment in 2008
Edited sentence: In recent years, some of these have been very controversial and high-profile, such as legalizing commercial gambling in 1993, Missouri Constitutional Amendment 2 (2006) (allowing the production of human embryos for stem cell research), Missouri Constitutional Amendment 2 (2004) (a  defense of marriage amendment prohibiting same-sex marriage), and an English-only amendment in 2008