Dear Nusrat Malik

My guess: Editorial style or Authors' choice or a Random unknown situation. There may be many reasons. Now, the question is why a scientist author would make that choice or let that happen. Unless you ask the author/s directly, you/we can only speculate about it. Speculation: when scientist authors (voluntarily) don´t include citations as they would do it in a regular peer-reviewed paper, they may want to write all their ideas down, even if there is nothing tangible to back them up. This is not necessarily wrong or bad. They may want you (the readers) to make the decision about whether a hypothesis, a method or any idea, is reasonable or valid, regardless of what other publications may say. Clearly, if the author is prestigious, it will be easy for him/her to impose ideas without supporting lit. So, read carefully.

It should have if the author cites others.