Hello. You have not informed the sentences or the sources to which this question refers, which makes it impossible for it to be answered accurately. However, I will try to help you in the best possible way.
If the writer wants to show the sources of information he used, he must present the bibliographic references of those sources. These references must follow a pattern called APA, which states that the sources of a survey must be presented, showing the following information, in the following order:
Author's last name + author's name + title of article or book + edition + place of publication + year of publication.