What, Where and Whence: Means for Improving Electronic Data Access. - Frits L. Engel; J. J. Andriessen; H. J. R. Schmitz (Int. J. Man Mach. Stud., 1983)

Expectations and Feedback in User-System Communication. - Frits L. Engel; Reinder Haakma (Int. J. Man Mach. Stud., 1993)

Improved efficiency through I- and E-feedback: a trackball with contextual force feedback. - Frits L. Engel; Peter Goossens; Reinder Haakma (Int. J. Hum. Comput. Stud., 1994)