Issue No. 04 - April (1979 vol. 1)
Akira Nakamura , Department of Applied Mathematics, Hiroshima University, Hiroshima, Japan; Computer Science Center, University of Maryland, College Park, MD 20742.
It is proved that the emptiness problem for deterministic bottom-up triangle acceptors (BTA's) over a single input symbol is recursively unsolvable. From this result, it is also shown that certain decision problems involving BTA's and BPA's (deterministic bottom-up pyramid acceptors) are unsolvable.
Akira Nakamura, "Some Decision Problems for Bottom-Up Triangle Acceptors", IEEE Transactions on Pattern Analysis & Machine Intelligence, vol. 1, no. , pp. 415-417, April 1979, doi:10.1109/TPAMI.1979.4766953