Correlation based on key tephra layers between the Ofuna-Koshiba Formations in the Yokohama district and the Kiwada Formation in the Boso Peninsula, central Japan.
BLOW, W. H. Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy. Proceeding of the First International Conference on planktonic microfossils (Geneva, 1967). 1969, 1, 199-422