Although he has retired, Dai Yuanzhi is never idle. The 64-year-old former China Youth Daily journalist has devoted more than 10 years to researching the history of Nanjing's biggest refugee camp,which housed more than 20,000 Chinese civilians during the 1937massacre in the city.

In his book 1937-1938 and the Atrocities of Humanity, Dai described the camp's foundation and activities, and introduced the name of Bernhard Arp Sindberg to the world.

Jing Shenghong, a Nanjing Normal University historian who specializes in studies of the Nanjing Massacre, described Dai as the "leading expert" about refugee camps during the atrocities. "He has uncovered lots of evidence about the Nanjing Massacre and filled in many blanks in historical research," he said.

Before the turn of the century, "Sindberg"was simply a name that appeared in a book written by John Rabe, the president of the Nanjing Safety Zone in1937,but Dai fleshed out the picture after researching the Dane's life and work in China.

"In the 1990s, researchers noticed that a German war file mentioned the Jiangnan Cement Factory," he said."In May 2000, shortly before he passed away, Gao Xingzu, a professor at Nanjing University, suggested that we should dig deeper into Sindberg's history. Both history and news rely on facts, so I decided to take over Gao's research and figure out what happened in the camp and what happened to Sindberg."

The project was a daunting one. Dai had to overcome the language barrier to search for Sindberg's relatives in Europe and raise funds for research.

"First, we found some descendants of Karl Gunther. They provided 41 photos. Later, we managed to contact Sindberg's sister and niece, who both provided a wealth of historical material."

Dai also took college students to remote villages to visit the surviving refugees, and analyzed all the historical materials he could find in Denmark, Germany and Japan.

"The younger generation should know about the history.

"As we grow old,we'll leave this world sooner or later, but we cannot take history with us," he said.