. . . "An xref to an organism taxonomy database, preferably NCBI taxon. This should be an instance of unificationXref, unless the organism is not in an existing database."^^ . "An xref to an organism taxonomy database, preferably NCBI taxon. This should be an instance of unificationXref, unless the organism is not in an existing database."^^ . "An xref to an organism taxonomy database, preferably NCBI taxon. This should be an instance of unificationXref, unless the organism is not in an existing database."^^ . . . . . . .