According to this
Aboriginal Australians, Pacific Islanders carry DNA of unknown human species, research analysis suggests
and according to this
The proportion of Neanderthal-inherited genetic material is about 1 to 4 percent [later refined to 1.5 to 2.1 percent] and is found in all non-African populations
Are these the only known 2 species whose DNA is present in modern humans, or are there more cases like these ones?