Question: Who was the cosmonaut that wrote about a difficult period onboard the Salyut 6?
About the article "International Space Station", section "Stress".

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Between 1971 and 1986, 48 individuals of eleven different nationalities visited the Salyut space stations.
Vladimir Dzhanibekov made the most visits to Salyut stations, with two trips to Salyut 6 and three to Salyut 7.
Georgi Grechko was the only cosmonaut to visit three different Salyut stations; Salyut 4, Salyut 6 and Salyut 7.
Svetlana Savitskaya, who made two flights to Salyut 7, was the only woman to fly as part of the programme. 
There has been considerable evidence that psychosocial stressors are among the most important impediments to optimal crew morale and performance.
Cosmonaut Valery Ryumin, wrote in his journal during a particularly difficult period onboard the Salyut 6 space station: “All the conditions necessary for murder are met if you shut two men in a cabin measuring 18 feet by 20 and leave them together for two months.”NASA's interest in psychological stress caused by space travel, initially studied when their manned missions began, was rekindled when astronauts joined cosmonauts on the Russian space station Mir.
Common sources of stress in early American missions included maintaining high performance while under public scrutiny, as well as isolation from peers and family.
The latter is still often a cause of stress on the ISS, such as when the mother of NASA Astronaut Daniel Tani died in a car accident, and when Michael Fincke was forced to miss the birth of his second child.
A study of the longest spaceflight concluded that the first three weeks represent a critical period where attention is adversely affected because of the demand to adjust to the extreme change of environment.
While Skylab's 3 crews remained one, two, and three months respectively, long term crews on Salyut 6, Salyut 7, and the ISS last about five to six months while MIR's expeditions often lasted longer.
The ISS working environment includes further stress caused by living and working in cramped conditions with people from very different cultures who speak a different language.
First generation space stations had crews who spoke a single language, while second and third-generation stations have crew from many cultures who speak many languages.
The ISS is unique because visitors are not classed automatically into 'host' or 'guest' categories as with previous stations and spacecraft, and may not suffer from feelings of isolation in the same way.
Crew members with a military pilot background and those with an academic science background or teachers and politicians may have problems understanding each other's jargon and worldview.
Soyuz T-11 was the 6th expedition to Salyut 7, and carried the first Indian cosmonaut to the Salyut 7 station.
Salyut 7 was unmanned after the undocking of Soyuz T-11 in October 1984 until Soyuz T-13 docked with the station in June 1985.
Salyut 7 developed problems during the unmanned time, which meant that the crew of Soyuz T-13 had to perform a manual docking and do repairs to the station. 
Soyuz 38 was a human spaceflight mission conducted by the Soviet Union during September, 1980.
The Soyuz spacecraft brought two visiting crew members to the Salyut 6 space station, one of whom was an Intercosmos cosmonaut from Cuba. 
Salyut 6 (DOS-5) (; ) was launched on 29 September 1977.
Salyut 6 was visited from 1977 until 1981 by 16 manned spacecraft, bringing five long-duration crews ("expeditions") and 11 short-term crews.
The very first long-duration crew on Salyut 6 broke a record set onboard Skylab, staying 96 days in orbit.
The short-term crews included foreign cosmonauts from the Interkosmos programme setting several firsts: the first citizen in space of a nation other than the United States or the Soviet Union, the first black and Hispanic person in space and the first Asian person in space.
The longest flight onboard Salyut 6 lasted 185 days.
The third long-duration Salyut 6 crew deployed a 10-meter radio-telescope antenna delivered by an uncrewed cargo spacecraft.
After Salyut 6 manned operations were discontinued in 1981, a heavy unmanned spacecraft called TKS, developed using hardware left from the canceled Almaz programme, was docked to the station as a hardware test.
Some unconfirmed reports say the station was functionally capable of even more missions, but combating the ever-increasing mold in living quarters was becoming impossible, and in practice caused the retirement decision.
Salyut 6 was deorbited on 29 July 1982.