Conservation of mass?

[christos]

Most places you look in books and online you will find that Lavoisier discovered the law of conservation of mass but I learned that Mihail Lomonosov a Russian chemist poet and astronomer discovered it before Lavoisier. I also found an article that states that Nasir al din tusi discovered it.then I found a web page that says Lucretius discovered it.If you type in Mihail Lomonosov Conservation of mass you will fine there are web pages that say he descovered it before Lavoisier.If Mihail Lomonosov discovered it first then why don;t they teach that in schools? Who really discovered the conservation of mass?
http://www.ehow.com/about_4568411_law-conservation-mass.html
http://en.wikipedia.org/wiki/Conservation_of_mass
http://english.turkcebilgi.com/Conservation+of+mass

"The law of conservation of mass was first clearly formulated by Antoine Lavoisier; in 1789, who is often for this reason (see below) referred to as the father of modern chemistry. However, Mikhail Lomonosov (1748) had previously expressed similar ideas and proved them in experiments. "

[teyo]

Mr. Lomonosov might not have reported them earlier. He must have reported it after Lavoisier reported his.