1. Ågren, A., 1967, The fractional Fix-Point method, FL Thesis (University Institute of Statistics, Uppsala).
2. Ågren, A., 1969, Fractional Fix-Point (FFP) estimation, in: Wold and Lyttkens, eds. (1969) Section 10, 37–38.
3. Ågren, A., 1970, Fractional Fix-Point (FFP) estimation, in: Mosbaek and Wold et al. (1970) Chapter 3.6, 129–136.
4. Ågren, A., 1972a, Extensions of the Fix-Point method, Published Doctoral Thesis (University of Uppsala, Uppsala).
5. Convergence analysis of the Fix-Point method based on pseudo-variables, Seminar Paper;Ågren,1972