  Cosmological solutions derived by Nariai and Tomita (1971) and by Starobinsky
(1980) are compared, and it is shown that the former derived de Sitter
expansion in the R^2 modified gravity (without cosmological constant) at the
earliest stage, and nine years later the latter derived the well-known
inflationary solution. Next the property of their simplified models is
described using the method of conformal transformations, and how the inflation
arises and the singularity is avoided is shown. Finally the initial and final
states of the inflation are discussed.
