Geodesic
Derivability of admissible rules
Zapiski Nauchnykh Seminarov POMI, Studies in constructive mathematics and mathematical logic. Part V, Tome 32 (1972), pp. 85-89 
G. E. Mints. Derivability of admissible rules. Zapiski Nauchnykh Seminarov POMI, Studies in constructive mathematics and mathematical logic. Part V, Tome 32 (1972), pp. 85-89. http://geodesic.mathdoc.fr/item/ZNSL_1972_32_a11/
@article{ZNSL_1972_32_a11,
     author = {G. E. Mints},
     title = {Derivability of admissible rules},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {85--89},
     year = {1972},
     volume = {32},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1972_32_a11/}
}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

A rule is admissilbe (conservative) if every deduction of its premises can be transformed into a deduction of the conclusion. A rule is (directly) derivable if there exists a derivation of its conclusion from the premises. It is known [2] that there exists a rule closed under substitution and admissible but underivable in the intuitionistic propositional caloulus (IPC). The main result: any admissible (in IPC) rule of the form $A_1,\dots,A_n\vdash A$ is derivable provided that at least one of the connectives $\supset,V$ does not occur in it. The result is the best possible as is shown by the rule (I).