  This work is a continuation of authors' research interrupted in the year
2010. Derived are recursive relations describing for the first time all
infinitesimal symmetries of special 2-flags (sometimes also misleadingly called
`Goursat 2-flags'). When algorithmized to the software level, they will give an
answer filling in the gap in knowledge as of 2010: on one side the local finite
classification of special 2-flags known in lengths not exceeding four, on the
other side the existence of a continuous numerical modulus of that
classification in length seven.
