Within the past week, many companies have left Russia over backlash from the country's invasion of Ukraine, most notably McDonald's, but several remain.

A Yale business school professor, Jeffrey Sonnenfeld, has shared a list of companies that remain operational in Russia, and though many have left the region since its initial publication, others have stayed.

As of Tuesday, multiple large companies remain operational in Russia as the economy collapses and the calls for peace continue. Casualties grow each day and more countries are calling for Russia to be investigated for war crimes.

Some have cited concerns about the welfare of the Russian people if companies that provide necessary and life-saving services decide to leave. For example, Pfizer announced that the company would continue operations that provide critical medicines to Russia.

CBS News reports that Abbott Labs, a multinational medical device and healthcare company, also remains in Russia despite pledging $2 million to humanitarian efforts in Ukraine. According to Sonnenfeld, Abbott Labs suspended “non-essential business activity.”

However, some companies remain despite their presence not being necessary. The list of companies still operating in Russia in some capacity includes direct sales giant Amway, Bridgestone, Cargill, Citigroup, General Mills, Nestle, Koch Industries, Halliburton, Herbalife Nutrition, Hyatt, Marriott, Leo Burnett and Subway.

Cryptocurrency companies have struggled with ‌whether to close Russian accounts as the ruble falls drastically. These companies have resisted efforts to close Russian accounts unless they are legally obligated to do so by sanctions.

Some notable crypto companies still operating Russian accounts include Kraken, Binance and Coinbase. However, Sonnenfeld told CBS that there is "no middle ground here." Sanctions are not effective without the backing of large companies, Sonnenfeld said.