Ian R. Porteous uses the three direct sums above, denoting them
Sum 41 | Direct current | direct current | direct action | The Sum of All Fears | Turbocharged Direct Injection | High-voltage direct current | Direct marketing | Yeung Sum | Joint Direct Attack Munition | Direct memory access | The Sum of All Fears (film) | Sum Mo Chikan | Portsmouth Direct Line | National Academy of Direct Taxes | International direct dialing | The Sum of Us | Supporters Direct | Sum-of-squares optimization | Sum of absolute transformed differences | Saab Direct Ignition | Memphis: Direct from Broadway | Direct-response marketing | Direct reduced iron | Direct Metal Laser Sintering | Direct metal laser sintering | direct marketing | Direct Factory Outlets | direct democracy | Direct-broadcast satellite |