I also cannot find that paper online but I did find a paper which reviewed that paper and came to a different conclusion.
Postilla Yale Peabody Museum No. 30
September 15, 1958 New Haven, Conn.
A NOTE ON THE FIRETHROAT AND THE BLACKTHROATED ROBIN
S. Dillon Ripley
While on a visit to the U.S.S.R. recently, I had the opportunity of examining two specimens of the small chat, the Black-throated Robin, collected by Berezowsky and Bianchi and described by them in 1891 as Larvivora obscura. Both are adult males in fully adult plumage and are in the Zoological Museum in Leningrad.
Also in the Leningrad, collection is an adult male specimen of 'Calliope' pectardens David. Due to the kindness of Dr. A. Ivanov, I was able to examine these specimens closely. Later in London I examined the series of pectardens and the single male obscura which have already been reported on by Goodwin (1956, Bull. Brit. Orn. CI. 74-75). Mr. H. G. Deignan has also kindly supplied me with information on the fine series of pectardens in the U. S. National Museum.
Goodwin and Vaurie (1956, Bull. Brit. Orn. Cl. 70: 141- lxl.), have published their comments on these two species, bringing forward the opinion that both were color phases of a single species. In connection with studies on the subfamily of the thrushes for the Peters' "Checklist, I was anxious to determine this matter to my own satisfaction.
The principal problem as to the identity or discreteness of these two populations is lack of specimens showing stages of plumage. In the British Museum and the U. S. National Museum collections there are fine series of pectardens from Yunnan, southeast Sikang and southeast Tibet. A single male adult pectardens perhaps a post-breeding season bird has been taken in southwest Shensi. There are many immature males, two presumed females (so identified), and a young male in the spotted plumage of the nestling. The specimens of obscura, however, are confined to adult males, so that the differences or resemblances between the two populations must be considered only as between the adult male plumages. These males of obscura come from southeast Kansu, and southwest Shensi in west China.
The obvious difference between the adult males is that the throat and breast are black in obscura, while in pectardens an approximately similar area is orange, and in addition, whereas both species have the sides of the neck black, there is a white patch on the side of the neck in pectardens. Goodwin and Vaurie's thesis (1956, tom. cit.) is that this color difference is not a difference in pattern, that, therefore, it is a simple genetic replacement, and that the species has a dimorphic breeding plumage, as has been noted in some species of wheatears {Oenanthe).
Examination of the specimens in Leningrad and other museums has inclined me to disagree. While extremely close, the patterns are different as the following sketch shows. …The physical measurements of these birds do not differ significantly. From the above it appears to me that these populations represent two distinct species, whose ranges may or may not be partly overlapping in northwest China. The northernmost species, obscura, is apparently more sedentary as indicated by the shape of the wing and indeed the paucity of specimens in collections. The more southern species, pectardens, indicates by the appearance of the wing and the occasional records of winter birds in Sikkim, Assam and northern Burma to the south of its usual range, that it is a more migratory species. In addition the minor differences of distribution of black on head, neck and sides of upper breast, serve to reinforce the more obvious, but more questionable from a genetic point of view, differences between orange and black throat patch and presence or absence of white neck spot. I believe that eventual examination of females and young of obscura will substantiate the distinctness of these two species.
http://archive.peabody.yale.edu/scipubs/bulletins_postillas/ypmP037_1958.pdf .