Original sentence: The above, plus Russian Manchuria, a region in Russia that stretches from the Amur and Ussuri rivers to the Stanovoy Mountains and the Sea of Japan.The part of Manchuria in China is commonly called Chinese  to contrast it with Outer Manchuria (see below)
Edited sentence: The above, plus Outer Manchuria or Russian Manchuria, a region in Russia that stretches from the Amur and Ussuri rivers to the Stanovoy Mountains and the Sea of Japan.The part of Manchuria in China is commonly called Inner Manchuria to contrast it with Outer Manchuria (see below)