“…The transformation can be operated with rigorous mathematical approaches, such as exact lumping methods Li and Rabitz, 1989;Li et al, 1994a), and approximate lumping Li and Rabitz, 1990;Li et al, 1994b;Tomlin et al, 1994;Wang et al, 1998). For example, during the development of RADM2 (Stockwell et al, 1990), the primary VOCs were lumped based on aggregation factors of their reactivity with OH radicals.…”