Hi @masudrana. Great article. I have a few suggestions though.

Information and pictures:
Wikipedia
Letters from the country and abroad
Internet

• This is not a proper way of citing references. You need to provide links so that any of your readers who are interested can refer to the original article. Same goes for the images' source. I've made an article regarding this topic before. You can click here to find out.

• This article is too long. Try to squeeze the information within 1000-2000 tops. It's difficult to focus on a lengthy article.

Please note that I'm not in any way, try to disapprove your work. You've done an excellent job here, but you can make it better. If you have any problem regarding STEM-related articles, you can join steemSTEM Discord Channel and we will be glad to assist you.