(1978). Economics letters. North Holland.
Dyfyniad Arddull ChicagoEconomics Letters. Amsterdam: North Holland, 1978.
Dyfyniad MLAEconomics Letters. North Holland, 1978.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.
(1978). Economics letters. North Holland.
Dyfyniad Arddull ChicagoEconomics Letters. Amsterdam: North Holland, 1978.
Dyfyniad MLAEconomics Letters. North Holland, 1978.