In this task, you are given two sentences in the English language and your task is to classify them into one of their discourse types. A discourse type is an indicator to classify the given two sentences on the basis of a co-text as well as a relevant context. There are 13 discourse types in total which are 'SINGLE_S_COORD', 'SINGLE_CATAPHORA', 'SINGLE_CONN_INNER', 'SINGLE_APPOSITION', 'SINGLE_VP_COORD', 'SINGLE_CONN_START', 'PAIR_ANAPHORA', 'PAIR_CONN', 'SINGLE_RELATIVE', 'SINGLE_CONN_INNER_ANAPHORA', 'SINGLE_S_COORD_ANAPHORA', 'PAIR_CONN_ANAPHORA' and 'PAIR_NONE'.

Sentence 1:Foo.secondlifeherald.com. 2010 - 02 - 04 . Sentence 2:Retrieved 2013 - 12 - 14 .
PAIR_NONE

Sentence 1:The presence of nitrogen dioxide is necessary for the reaction to proceed at a reasonable rate . Sentence 2:The process is highly exothermic , and a major consideration of the design of the chambers was to provide a way to dissipate the heat formed in the reactions .
PAIR_NONE

Sentence 1:Writers like Faulkner , who won the Nobel Prize in Literature in 1949 , also brought new techniques such as stream of consciousness and complex narrative techniques to their writings . Sentence 2:nan

SINGLE_RELATIVE