Fix #761, removed unclear sentence in section 9.2

index.bs

@@ -3130,7 +3130,7 @@ The figure below shows the linking scheme among IDs in the obu_header or OBU pay
 In the figure above,
 - The [=Codec Config OBU=] with [=codec_config_obu/codec_config_id=] = 0 is providing its [=codec_id=] and [=decoder_config=].
 - The [=Mix Presentation OBU=] with [=mix_presentation_id=] = 21 is saying:
-	- There are two [=Audio Element=]s (with [=audio_element_obu/audio_element_id=] = 11 and 12) which need to be mixed. The [=mix_presentation_obu/audio_element_id=] = 11 and the [=mix_presentation_obu/audio_element_id=] = 12 are linked to the [=Audio Element OBU=]s with [=audio_element_obu/audio_element_id=] = 11 and [=audio_element_obu/audio_element_id=] = 12, respectively.
+	- There are two [=Audio Element=]s (with [=audio_element_obu/audio_element_id=] = 11 and 12) which need to be mixed.
 		- There are [=Parameter Block OBU=]s with [=parameter_block_obu/parameter_id=] = 32 to be used for mixing the [=Audio Element=] with [=audio_element_obu/audio_element_id=] = 11.
 		- There are [=Parameter Block OBU=]s with [=parameter_block_obu/parameter_id=] = 33 to be used for mixing the [=Audio Element=] with [=audio_element_obu/audio_element_id=] = 12.
 	- There are [=Parameter Block OBU=]s with [=parameter_block_obu/parameter_id=] = 34 to be used for mixing the two [=Audio Element=]s.