Google them and the words 'bravery', 'audacity', and 'justice' are among the first to pop up. Thousands of articles, stacks of books and scores of songs – even one by U2 - have been dedicated to them.

Letter from Mothers of Plaza de MayoThe Mothers of the Plaza de Mayo is an association of Argentine women whose children were "disappeared" from 1976-1983 during the country's notorious "Dirty War".

Human rights groups estimate that over 30,000 people were kidnapped and murdered during this time in Argentina - one of South America's most brutal episodes of state-sponsored repression.

The group's name comes from the square where they gathered on an April day in 1977. With public gatherings illegal at the time, the police tried to move them on but they peacefully resisted, linking arms and walking together around the square. This was the action that established the Mothers of the Plaza de Mayo Association.

Tirelessly demanding justice for their children over four decades, hundreds of former military officials have been convicted for their role in the abductions. But where many of the Disappeared are buried is unknown.

The few surviving Mothers are very old now with many ailments, but regardless they march every Thursday in honour of their loved ones.

These women have now written a letter to President Vladimir Putin of the Russian Federation as the Mothers want the Arctic 30 to come home.

Their request comes as the mother of detained Turkish Arctic 30 activist Gizem Akhan has written an open letter calling for her countrymen and women to support her daughter.

Gizem's mother, Tülay Akhan, writes about seeing pictures of her daughter standing "in court in handcuffs" and giving her testimony from "inside a cage. All because she was peacefully protesting against a company that is trying to drill in the Arctic sea, Gazprom."

She continues, saying the Arctic 30 "all took a step for the future of this Earth, marched on and stood up for something."

"Each child is precious to their mother. For me, Gizem is without equal. She is without equal. She has love for all and believes in the right cause, with hope that is blindingly green," writes Tülay.

"The good always wins, all we need to do is to believe that we can."

Gizem Akhan on the Arctic Sunrise in Norway. 08/11/2013 © Will Rose / Greenpeace

Tülay ends her correspondence by quoting a letter from her daughter, Gizem: "We read letters yesterday from people all over the world. South Africa, America, Mexico... We feel more relaxed when we hear about the support we get, and how much people are working to free us. Let me know that you are well, that you support us. This is all that I need right now."