Task: Question Answering
Input (English): Passage: On the Greek island of Kalokairi, 20-year-old bride-to-be Sophie Sheridan reveals to her bridesmaids, Ali and Lisa, that she has secretly invited three men to her wedding without telling her mother, Donna. They are the men that her mother's diary reveals could have been her father: Irish-American architect Sam Carmichael, Swedish adventurer and writer Bill Anderson, and British banker Harry Bright. She dreams of being given away by her father at her wedding, and believes that after she spends time with them she will know which is her father.
Sophie's mother Donna, who owns a villa and runs it not very successfully as a hotel, is ecstatic to reunite with her former Dynamos bandmates, wisecracking author Rosie Mulligan and wealthy multiple divorcée Tanya Chesham-Leigh, and reveals her bafflement at her daughter's desire to get married. Donna shows off the villa to Rosie and Tanya. The three men arrive and Sophie smuggles them to their room. She doesn't reveal that she believes one of them is her father, but does explain that she and not her mother sent the invitations. She begs them to hide so Donna will be surprised by the old friends of whom she "so often" favorably speaks. They overhear Donna working and swear not to reveal Sophie's secret.
Donna spies them and is dumbfounded to find herself facing former lovers, demanding they leave. She confides in Tanya and Rosie that she truly does not know which of the three fathered Sophie. Tanya and Rosie rally her spirits by getting her to dance with an all female ensemble of staff and islanders. Sophie finds the men aboard Bill's yacht, and they sail around Kalokairi, telling stories of Donna's carefree youth. Sophie plans to tell her fiancé Sky about her ploy, but loses her nerve. Sky and Sophie sing to each other, but Sky is abducted for his bachelor party. 
Question: What are the full names of the persons who swear not to tell Sophie's secret?
Output (English): Bill Anderson.