This chapter deals with generalized forms of mixed problems, which can be expressed in terms of operators in the following forms: [ A B ∗ B − D ] , [ A C ∗ B 0 ] , [ A B 1 ∗ B 2 ∗ B 1 0 0 B 2 0 0 ] . https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429507069/af768ad5-21aa-4c7b-88c6-5318b65e2dde/content/umath11_1.jpg"/> The first two appear naturally when considering mixed formulations of reaction-diffusion and convection-diffusion problems. The third structure can be considered as a simple mixed problem where the side restriction takes values in a product space. As the cherry on top of this chapter we will include a partially uncoupled formulation of the Stokes-Darcy flow problem, which we will approach using two reorderings of the associated matrix of operators.