On the Use of Gravitational Vector Potenctial in the Relativity theory of Birkhoff
On the Use of Gravitational Vector Potenctial in the Relativity theory of Birkhoff - Helsinki : Suomalainen Tiedeakatemia, 1957. - 23 p. ; 21 cm. - Annales Academiae Scientiarum Fennicae ; 228 .