Question: China has been negotiating the specifics of its disputed borders since what year?
About the article "China", section "Territorial disputes".

Candidate passages:
In addition to claiming all of Taiwan, China has been involved in a number of other international territorial disputes.
Since the 1990s, China has been involved in negotiations to resolve its disputed land borders, including a disputed border with India and an undefined border with Bhutan.
China is additionally involved in multilateral disputes over the ownership of several small islands in the East and South China Seas, such as the Senkaku Islands and the Scarborough Shoal.
Post referendum.
Crisis talks.
The political crisis in Niger appears deadlocked since the disputed referendum and election.
General Abdulsalami Abubakar of Nigeria, a mediator appointed by the Economic Community of West African States (ECOWAS), has been negotiating a power-sharing arrangement. 
The Federal Border Guard Service (FPS) has been part of the FSB since 2003.
Russia has of sea and land borders, of which is with Kazakhstan, and with China.
One kilometer (1,100 yd) of border protection costs around 1 million rubles per year. 
Under a 2012 deal mediated by the United States, China and the Philippines promised to withdraw their forces from the shoal until a deal over its ownership could be reached.
The Philippines complied with the agreement and withdrew.
China, however, did not abide the agreement and maintained its presence at the shoal, effectively militarizing it.
Philippine president Benigno S. Aquino III later compared China's behavior to Nazi Germany's annexation of Czechoslovakia.
By July 2012, China had erected a barrier to the entrance of the shoal, according to the Philippine Department of Foreign Affairs.
Since then, vessels belonging to the China Marine Surveillance and Fisheries Law Enforcement Command have been observed in the nearby disputed shoal and Chinese government vessels have been turning away Filipino vessels sailing to the area.
In response, the Philippines has stated that it would be preparing to resend vessels to the shoal, in what has been described as a "cold standoff".
By January 2014, China continued to maintain a presence within the shoal, among heightened tensions regarded a new law which requires non-Chinese fishing boats to seek permission from China when in the South China Sea, however Philippine fishing boats were able to fish around the shoal without Chinese interaction. 
Kalapani (कालापानी) is an area under territorial dispute in Darchula District, Nepal and Pithoragarh district of India.
Although claimed by Nepal, Kalapaani has been occupied by India's Indo-Tibetan border security forces since the 1962 border war with China.
Nepal claims that the river cited in the 1816 treaty should be followed all the way to its Himalayan source as the boundary, rather than the ridge line east of the river claimed by India.
The river borders the Nepalese zone of Mahakali and the Indian state of Uttarakhand.
The Sugauli Treaty signed by Nepal and British India in 1816 utilizes the Kali River as Nepal's western boundary with India.
Subsequent maps drawn by British surveyors show the source of the boundary river at different places.
This discrepancy in locating the source of the river led to boundary disputes between India and Nepal, with each country producing maps supporting their own claims.
The Kalapani River runs through an area that includes a disputed area of about 400 km² around the source of the river although the exact size of the disputed area varies from source to source.