If a whitepaper is inadvertently missing a quotation or citation, the author should promptly fix it once this is pointed out. A number of missing citations is not necessarily an indication the project is a scam. I think ultimately, good judgment needs to be used when evaluating if a project is a scam based on a whitepaper and missing citations. You can ask if the missing citations substantially change the chances of success in the eyes of a reasonable person. You can ask if the missing citations are indicative that the project is a substantial copy of another project with few substantive details changed.