DigimonWiki:Digivolution References/Adventure:

"Tokyo Digital Crisis" [01]
 * Koromon > Agumon > Greymon
 * Argomon (Fresh) > Argomon (In-Training) > Argomon (Rookie) > Argomon (Champion)

"War Game" [02]
 * Argomon (Champion) > Argomon (Ultimate) > Argomon (Mega)
 * Greymon + Garurumon > Omnimon

"Birdramon Soars" [04]
 * Botamon > Koromon
 * Biyomon > Birdramon