There is a paucity of epidemiological studies of Tourette syndrome; ascertainment bias affects clinical studies. Medical sources sometimes refer to sampling bias as ascertainment bias. The result is a form of ascertainment bias. Specifically, it arises when there is an ascertainment bias inherent in a study design. This dilemma is known as an ascertainment bias. He discovered the answer to several seeming paradoxes caused by ascertainment bias. Tracing is impossible only when the means of ascertainment fail. To each certificate of vote, a certificate of ascertainment is annexed. In addition, there was a uniform rent ascertainment scheme contained in section 12. The following results are from these Certificates of Ascertainment. Ascertainment of the location was facilitated by the utilization of GIS technology and remote sensing. "Secret Essence Tantra", "Treasury of Precious Qualities", "Ascertainment of the Three Vows" and other topics.