Perhaps you should try some spelling variations:
orta » aorta, ohta, orts
porta » paorta, pohta, ports, aorta, porto, parta, posta
portal » paortal, pohtal, portsl, aortal, portol, partal, postal, portable
ortad » aortad, ohtad, ortsd, orcad
port » part, post
orca » dorca, orcad, ohca
marc » mac, mark

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: modified ((((((orta OR porta) OR port) OR portal) OR orca) OR marc) OR ortad) estimation algorithm~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "modified ((((((orta OR porta) or port) or portal) or orca) or marc) or ortad) estimation algorithm~".
• Adding a wildcard symbol may retrieve word variants: modified ((((((orta OR porta) or port) or portal) or orca) or marc) or ortad) estimation algorithm*.