It can be very difficult to determine a surname in Bulgarian and it is a good idea to do some extra work. The forms of the name in the copyright statements are generally fuller forms and guidance should be sought concerning which name is the surname, e.g.

NAFL836030
100 10 Choroleeva, Mariia
670 Krumova, L. Sukrashtavaneto i suskrashteniiata v bulgarskiia ezik, 1982:_t.p. (Mariia Choroleeva) verso t.p. (copr Mariia Georgieva Choroleeva)

but

NAFL 836032
100 10 Krumova, Liliia
400 10 TSvetkova, Liliia Krumova
670 Her Sukrashtavaneto i suskrashteniiata v bulgarskiia ezik, 1982:_t.p. (Liliia Krumova) verso t.p. (copr. Liliia Krumova TSvetkova)