Obliquus Capitis Superior
The obliquus capitis superior is a member of the suboccipital group of muscles along with obliquus capitis inferior, rectus capitis posterior major and rectus capitis posterior minor. It is narrow below, wide and expanded above, and is lateral to the semispinalis capitis. It forms the superolateral border of the suboccipital triangle.
The obliquus capitis superior is located laterally in the suboccipital compartment.
Between the superior and inferior nuchal lines of the occipital bone
Suboccipital nerve or dorsal ramus of cervical spinal nerve (c1)
Is a postural muscle that monitors the position of the head. 
Bilaterally, they extend the head; unilaterally, they laterally flex the the head to the same side as the muscle.
The actions of trapezius, sternocleidomastoid and other larger muscles that move the head are refined by the relatively small suboccipital triangle muscles.
Recent Related Research (from Pubmed)
- Henry Gray: Anatomy of the Human Body [monograph online]. Philadelphia: Lea & Febiger; 1918 [cited 2015 Mar 30]. Available from: Bartleby; New York: 2000. fckLRhttp://www.bartleby.com/107/116.html
- Wheeless III, CR. Obliquus capitis superior [Internet] 2011 [cited 2015 Mar 30]. Available from: http://www.wheelessonline.com/ortho/obliquus_capitis_superior_1
- Obliquus capitis superior [Internet]. 2015 [cited 2015 Mar 30]. Available from: http://www.anatomyexpert.com/structure_detail/5212/