讲座内容：

In this talk, we consider the constructions for group divisible packings of type g^u with block size four (4-GDPs for short). A maximum 4-GDP of type g^u contains the largest possible number of blocks. Based on recursive constructions, we establish a framework to construct maximum 4-GDPs of type g^u. In the process, direct constructions on several key auxiliary designs are displayed by choosing appropriate automorphism groups. Eventually, the sizes of maximum 4-GDPs of type g^u are determined for all positive integers g and u, only leaving a small fraction of possible exceptions unresolved.