Here is an English article describing LGL's drug test issue in 1999-2000.
Liu's athletic career wasn't always smooth. In 1999, he failed a drug test but was later clear of doping suspicions after a lengthy battle to prove his innocence. "I feel so relieved," said Liu after hearing the news. "You can hardly imagine what a kind of life I led in past six months."
After a test in a Dutch laboratory suggested an "elevated value of epitestosterone", Liu had been under great pressure. "I didn't take anything illegal, but I didn't know how to explain or convince others. I couldn't sleep well, often jolted awaken by bad dreams," Liu said.
The International Table Tennis Federation ( ITTF) cleared Liu's name after a three-month-long investigation showed "no evidence for exogenous origin of epitestosterone" in Liu's samples and there was "no doping offense".
Liu tested positive on August 8, 1999, the day he won the world singles championship in Eindhoven. One day earlier, he tested negative after taking the men's doubles event with Kong Linghui. ITTF didn't notify Liu of his positive test until October 24, 1999, when Liu was playing in the Austrian Open.
"It was shocking," Liu recalled. " 'You are finished', I told myself. I didn't know what to say, what to do. I called the Chinese Table Tennis Association (CTTA) and they said they trusted me."
Liu took two unannounced tests by the ITTF investigative officials on February 2 and 7. Both tests cleared Liu, said then CTTA general secretary Yang Shu'an.
"ITTF has used the most advanced method of doping check and they have proved Liu's innocence, " said Yang. Another CTTA official said the world ruling body of the sport had used "IRMS" -- Isotopic Ratio Measurements, to test Liu's samples.
"We've never lost trust in Guoliang," said then Chinese head coach Cai Zhenhua. "We let him play the final of the world team championships because we believe he is clean."
China lost to Sweden 3-2 in the men's final in Kuala Lumpur in February 2000, as Liu lost to both Waldner and Jorgen Persson.
In the 2000 Olympics, Liu shaved his head for a new start and took a singles bronze medal. "That bronze was more important to me than the two golds I won in Atlanta," Liu said.
http://sports.sina.com.cn/others/pingpang/2016-02-27/doc-ifxpvysx1704500.shtml
Another article in Chinese when LGL led CNT to 2016 WTTTC in Kuala Lumpur, the same place where he lost to both JO Waldner and Persson and CNT lost to Sweden 16 years ago. That was the first time he lost to JO Waldner (he beat JO Waldner 6 times before) and he once had 3 set points. He said he had huge pressure since he was notified of being positive of epitestosterone after he won 1999 WTTC and became the first Chinese grand slam winner. He barely had his mind on the table, always worried that his career was ruined if he could not prove innocent. For half a year, he almost broke down, he lived alone, stayed up till 3-4am in the morning and got up at 7 am, waiting for ITTF spot drug test every 3 month. No drinking, no eating till 10 pm and he had to go to training as nothing happened because other players did not know his case. He thought he would not be selected for 2000 WTTTC because if he was still positive, the result of CNT would be canceled. But head coach Cai Zhenhua had faith in him and put him on the lineup. After the final of 2000 WTTTC, other CNT players got to know that LGL had drug test issue and ironically ONE WEEK AFTER 2000 WTTTC, ITTF officially announced that LGL was clean -- they got the results way before WTTTC and did not release it. LGL said the pressure he experienced from the drug test was way much more than playing in Olympic Games.