I play this system after 1NT opening with various partners. Depending on system and position, 1NT can be 15-17, 14-16 or 12-14. The system is the same, but of course you adjust as responder what hands are is GF, INV or weak.

The only thing which is somehow unusual (at least between Romanian experts) is the 2♠ response, which is transfer to clubs (normal) OR invitation to NT without four card major. This means 2♣ stayman is always with at least one four card major. This trick is borrowed from the Polish bridge school.

Answers to 1NT:

• 2♣ = stayman with al least one major. can be weak (garbage stayman, to stop in 2♦/♥/♠). it also includes 5♠ + 4♥ INV
• 2♦ / 2♥ = transfers
• 2♠ = transfer to club OR BAL INV
• 2NT = transfer to ♦
• 3♣ = 55 minors, INV (it just seems more useful than weak, to play with 55 minors)
• 3♦ = 55 minors, GF
• 3♥ = singleton ♥, 54 minors, 3 spades
• 3♠ = singleton ♠, 54 minors, 3 hearts (we jump in SHORT suit, not in 3 card one because we want opener to be declarer in a suit contract)
• 3NT = to play
• 4♣ = transfer to ♥
• 4♦ = transfer to ♠
• 4♥ / 4♠ = to play
• 4NT = quantitative
• 5♣ / 5♦ = to play

With both majors (some sequences are quite unusual, read CAREFULLY):

• very weak: stayman, then pass (or 2♥ after 2♦)
• 54 GF: stayman, then after 2♦ jump in the 4 card major (Smolen)
• with 5♠ + 4♥ INV: stayman, then after 2♦ - 2♠
• with 5♥ + 4♠ INV: transfer to hearts then 2♠
• 55 majors, INV: transfer to ♠ then bid 3♥
• 55 majors, slam INV: tranefer to ♥ then bid 3♠ (then, 3NT=2-2 in majors, 4♣=we play hearts, 4♦=we play spades, 4♥/♠=to play, refuses slam invitation)
• 55 majors, just game: transfer to ♠, then bid 4♥

Slam INV after stayman, with major fit: responder bids the OTHER major on level 3:

1NT - 2♣ - 2♥ - 3♠ = slam INV in ♥, denies splinter in ♣/♦
1NT - 2♣ - 2♠ - 3♥ = slam INV in ♠, denies splinter in ♣/♦

With 5m+4M, normal stayman sequences:

1NT - 2♣ - 2♥ - 3♣ = 5 clubs, 4 spades, GF. if responder had hearts, we should gave fit imediately (see above if slam INV).

After minor suit transfers, new suits at level 3 by responder shows singletons:

1NT - 2♠ - 2NT - 3♥ = clubs + singl ♥
1NT - 2♠ - 3♣ - 3♦ = clubs + singl ♦

After the dual 2♠ response, opener acts in first instance as over BAL INV, i.e bids 2NT if he would reject invitation (minimal) and 3♣ if he accepts. then:

1NT - 2♠ - 2NT - pass = i was BAL INV, we play 2NT
1NT - 2♠ - 2NT - 3♣ = i have clubs, weak
1NT - 2♠ - 2NT - 3♠ = i have clubs, spade singl (see above), slam INV
1NT - 2♠ - 2NT - 3NT = clubs, no singleton, passable, mild slam INV
1NT - 2♠ - 2NT - 4♣ = clubs, no singleton, serious slam INV
1NT - 2♠ - 3♣ - pass = clubs, weak
1NT - 2♠ - 3♣ - 3NT = i have BAL INV, no clubs
1NT - 2♠ - 3♣ - 3♦ = clubs, ♦ singl, slam inv (see above)
1NT - 2♠ - 3♣ - 4♣ = i have clubs, slam INV, no singl

After the 4♣/4♦ super-transfer (opener just make the transfer, NEVER super-accepts with the intermediate step), 4NT is KCBW. As opposed to 2 level transfer followed by 4NT which is quantitative.

After 2♦/2♥ tranfer

• we play just one super-accept, level 3 in responder suit, with 4 card fit (and no 4333). Thus, there are NO re-transfer sequences here.
• if opener simply transfers, 3-new-suit-below-transfered-suit is natural, GF. with an INV hand and 5 card only major, responder may use 2NT, which is natural, INV.
• after 2♦ heart transfer, 2♠ is 5♥ + 4♠ INV. 3♠ is 55 majors, slam INV (see above)
• 4♣/♦ is splinter (note that jump in other major is NOT splinter)

special running sequences (no matter what double is - this is more useful when weak NT, but we play the same over strong NT):

• pass = to play. subsequent doubles are penalty proposal.
• RDBL = i have a single suiter, please bid 2♣
• 2x = dont style
• 2NT = GF, freak hand
• 2♠/3x = to play
• 4♣ / 4♦ = hearts/spades super-tranfer

• see above if they double
• if the overcall is 2NT or lower, the 4 level super-transfers are in place (4♣ → hearts, 4♦ → spades)
• if the overcall is 2♣, all systems on (if 2♣ shows clubs, DBL is take-out/stayman). 1NT - (2♣)* - DBL=stayman
• if the overcall is 2x, 2NT/3x from simple lebensohl. transit via 2NT to show stopper in opps suit. IMPORTANT: 1NT - (2x) - 3NT=denies stopper, denies other(s) major!
• if the overcall shows 2 KNOWN suits (like 2♣/2♦ = both majors), CUE shows stopper. jump CUE=singleton. if the overcall shows 1 KNOWN suit, lebensohl applies
• if the overcall show the bid suit (and others or not), double is take-out
• if the overcall doesn’t show the bid suit (like 2♦=both majors or 2♦=one unknown major), pass then double penalty proposal. direct double shows the doubled suit (1NT - 2♦=both majors - DBL=I have some diamonds).

• direct action by opener promises fit:

1NT - (p) - 2♥ - (DBL)
2♠ = fit 3

1NT - (p) - 2♥ - (2♠)
DBL = fit 3

• RDBL by opener is to play, with 5 card suit:

1NT - (p) - 2♥ - (DBL)
RDBL = ! I have 5 hearts

• if 2♣ stayman is doubled, pass promisses stopper in clubs (but no 5 cards). responder may re-stayman with RDBL.
• RDBL by responder is re-stayman / re-transfer:

1NT - (p) - 2♣ - (DBL)
pass - RDBL = please answer to stayman

1NT - (p) - 2♥ - (DBL)
pass - (p) - RDBL = please do the transfer

This last position should be refined. Which is the difference between a direct 3♣ and a 3♣ after RDBL - forced transfer?

• if they double the dual 2♠ (BAL INV or clubs) answer: RDBL shows 5 spades. pass=minimal, no stopper in spades, 2NT=minimal + spade stopper. 3C=maximal (with or without spade stopper), now 3S just ask about spade stopper, with a balanced hand (no longer singleton).